First of all, a philosophy I have about Magic. I don't really believe in the great players of Magic "creating" decks like Fish-Opposition that Alex Borteh used to such great effect in Worlds, nor do I believe in the great thinkers of Magic like Jay Schneider "creating" the thing we now call the mana curve, where you play lots of little guys, less medium, and few large guys so that you can use all your mana every turn.
Instead of "creation", I like to think of Magic deck building and theory as a sort of "discovery". For every metagame, for every card set, the decks already exist just waiting to be discovered. Instead of creation, I see Magic deck builders and theorists more like scientists discovering pre-existing facets of nature.
Two of the more basic forces in Magic are tempo and card advantage.
The pertinence of this to the idea of tempo is that I don't feel that I'm inventing the idea of tempo; it already exists. What I'm doing is trying to find out what tempo is and finding a way to use this idea to the utmost to make new and powerful decks in both Limited and Constructed. I also feel that while there might be an alternative idea of what "tempo" means, I don't think that both of them can be right. It's certainly possible I don't have the perfect idea of what tempo means in Magic, but it's not just a simple definition I thought up, but something real that people already use.
Two of the more basic forces in Magic are tempo and card advantage. Card advantage is simple, you draw extra cards or somehow two for one your opponent some way.
Tempo is a much more slippery idea. Tempo is time, and what is not immediately obvious to some people is that time is equivalent to mana.
Suppose you tap and summon a Grizzly Bear. Then your opponent taps and summons a Gray Ogre. The Grizzly Bear deck has gained a tempo advantage. It has used less mana for what is essentially the same thing.
Now suppose the Gray Ogre deck uses Repulse to put a Grizzly Bear back into the opponent's hand and then Mr. Gray Ogre attacks. Repulse is a card people have been using in IBC as a "tempo" card, but in this situation, the Repulse is not gaining tempo. It is losing tempo.
The reason is that Repulse costs to put Grizzly Bear back in the hand, but next turn Grizzly Bear will be cast for only . That's a ratio of 3:2.
If both players have six mana and Gray Ogre/Repulse man has infinite Repulses, while Grizzly Bear man has infinite Grizzly Bears, each turn Gray Ogre man will bounce two Bears while Grizzly Bear man will play three back, netting him a gain of one Bear each turn.
It's all in the mana.
In IBC right now, decks have lots and lots of those little 2/2 guys for 2 mana. Does this means that Repulse isn't that good? If you are looking at the early game then yes, Repulse is not very good. It loses you tempo to be bouncing your opponent's bears. Your opponent will get more guys out and if it's a pure race with just bears he will win.
However, there's more to Repulse than that. In some situations Repulse can in fact be used to gain tempo. For the sake of simplicity, let's assume nothing of importance is drawn from the Excludes and Repulses or top of the deck during this mini-game.
In hand: 4x Exclude
In play: Bear, Bear, 4x land
In hand: 1x Exclude 1x Bear, 1x Repulse
In play: Bear, Bear (both tapped from attacking last turn), 4x land
In this situation both players have 4 lands in play 2 bears in play, while both have Exclude in hand. In this case, gaining tempo is not a simple matter. Gaining tempo here is all about finding ways to use your mana effectively while your opponent wastes his by not having an opportunity to cast a spell at the right time.
Player A has nothing so he has to say attack, then done. Player B can use Repulse during the attack phase, but if he does that Player A can just replay the bear. What if Player B waits until the end of Player A's turn and then Repulses a bear? Here, he has used the mana efficiently, and Player A has 4 mana untapped-all his mana for the turn unused.
Now Player B can untap and attack, but he doesn't immediately play his bear. He just waits, because he doesn't want to run into an Exclude. He has an advantage now with two bears vs. one in play.
Player A can cast his bear, which Player B answers with Exclude.
Player B now untaps and casts his third bear, and with Player A only having 2 mana up he can't prevent the bear from being cast.
Player A wasted entire turns without using his mana. Player B on the other hand used his mana every turn. He gained a huge amount of tempo. The effect of the tempo gain in this mini-game is that at the beginning Player A and Player B stood at 2 bears in play apiece while at the end Player B was ahead three bears to one.
Now normally if you do things like Repulse a 2/2 that cost 2 mana and then Exclude him, you're going to lose the tempo race. In this situation, even though you are using 3 mana and your opponent has been using 2 mana, the player with the relatively mana inefficient spells has been gaining tempo because his mana has been used at a better time.
Now notice something about Exclude. The main reason it is so good is not because it necessarily gains you tempo, but because it gains card advantage.
Here's an obvious way for Repulse and Exlude to gain tempo:
U-w with 5 mana available, Repulse, Exclude, 2 bears in hand.
Cast bear, leave 3 mana up.
R-g with Skizzik in hand.
Cast Skizzik with kicker. U-w Repulses Skizzik.
U-w casts other bear, leaves 3 mana up.
R-g casts Skizzik again with kicker, U-w Excludes Skizzik.
In this situation, r-g used up ten mana and with a +0 card gain, while u-w gained 2 creatures in play, and had net +1 card gain (all the cards here were neutral except Exclude which gained a card).
Repulse in this situation gained 2 mana because it was used on a Skizzik which costs more than the Repulse, and at the end of this minigame you can see u-w has gained tremendous tempo from it, with u-w having two creatures in play to r-g's none.
I have a feeling people are playing Repulse too much in IBC right now...
So, we have seen the three situations. In the first, Repulse wasn't so good, because the opponent only had bears, in the second, both players had only Bears, but by timing his spells well, the player with Repulse still gained tempo by forcing his opponent to be unable to use his mana. In the third, Repulse was used on a more expensive creature and gained significant tempo.
I have a feeling people are playing Repulse too much in IBC right now. The reason they play it is either from copying other people's decks, or because they have a misguided notion that it gains them tempo. Remember it's not bounce that makes tempo, it's mana efficiency. If one player has Swords to Plowshares and the other has Repulse, the person with Swords to Plowshares is going to gain a tempo advantage because his creature elimination spells are so cheap. Repulse really shines when your opponent plays creatures that cost more than 3, (or to save one of your own creatures from a removal spell, but that is more about card advantage than tempo).
In IBC right now, everywhere you see decks made mostly of these 2/2 for two mana guys, all kinds of bears with special abilities, and it's extremely hard to do what I did in situation 2, that is gain some sort of tempo advantage when your opponent only has these bears. Against red-green, Repulse is very good against Skizzik. The problem of course is that most of red-green's creatures only cost two mana and you end up losing because your Repulse is more expensive than him recasting his guys. The real bulkwark of the w-u in the current IBC format against other fast decks is not playing lots of Repulses but playing lots and lots of bears. Besides you can't Repulse a Voice of All if it gains protection from blue.
Not usually a good idea to Repulse a Titan
One general rule about tempo is that you can normally give up card advantage to gain tempo or you can give up tempo to gain card advantage. Sometimes cards give you both tempo and card advantage. These cards are normally very powerful.
If you use a Dark Ritual to power out a Phyrexian Scuta on turn two you have given up a card (the Dark Ritual) to gain tempo.
On the other hand, if you cast a Jayemdae Tome, then use it for a few turns, you have been giving up tempo in order to draw cards.
One card which can gain both tempo and card advantage is Wrath of God. If Player A has, for instance, three bears in play and Player B casts Wrath of God, he has used four mana compared to Player A's six, a tempo advantage of two mana, and he has also used one card (the Wrath) to Player A's three cards, giving the equivalent card advantage of Ancestral Recall in addition to the tempo. That's a tremendous swing.
Notice by the way, if Player A only has two bears in play, the tempo is even and the Wrath of God only gives a 2 for 1. It might not seem like much, only playing out 2 creatures instead of 3, but if you compare the tempo and card advantage, the jump from 2 to 3 is a huge difference when Wrath of God is involved. One last point in this Wrath of God example: If Player A casts out the two bears, and then instead of casting the third bear, just lets the mana sit unused in fear of Wrath of God, then Wrath of God can still gain a tempo advantage, because it forces Player A to not use his mana. In a situation like this where Player A's mana sits unused all the time, he isn't trying for the bum rush, but conserving his resources, and instead of a purely tempo game he is trying to prevent too much card disadvantage when Wrath goes off.
At Worlds this year, one of the best plays the red-black deck could make against the u-g
Saproling/Opposition decks was Ritualing out a Plague Spitter. Normally, a Ritual will certainly cause card loss in exchange for the tempo gain, but the u-g decks had creatures all of a toughness 1. So not only is there a tempo gain, but also virtual card advantage from that first turn Plague Spitter. The combination of both tempo gain and card advantage is a huge edge and was key to Tom van de Logt winning Worlds.
Now finally to return to IBC again, my favorite deck in the format is Pat Chapin's r-u-b deck, which is built almost entirely of tempo and card advantage cards.
4 Shivan Reef
4 Salt Marsh
4 Urborg Volcano
4 Blazing Specter
4 Ravenous Rats
3 Flametongue Kavu
4 Fact or Fiction
3 Yawgmoth's Agenda
2 Trench Wurm
1 Crosis, the Purger
1 Flametongue Kavu
Perhaps the most overlooked card right now in IBC is the all star in draft, the Flametongue Kavu. At 4/2, he is a meaty creature on his own, but he only needs to kill a random bear - any creature at all - for him to gain not only card advantage, but a significant tempo advantage.
Void is another overlooked card in IBC. When your opponent has all bears, and your best creatures cost 4 mana, you can gain significant card advantage and tempo advantage when this is played. Rats are two for one, here you gain no tempo, merely card advantage. Rats are very good against 1 toughness creatures like Blurred Mongoose and Raging Kavu, better in the early game than Nightscape Familiar and especially good when you recur them via Yawgmoth's Agenda.
Notice here how Terminate is one mana cheaper than the often-used Repulse, and as such much more often can gain tempo than Repulse. It isn't bounce that makes tempo, it's the relative mana costs each player is using for his spells. The Chapin deck has 4 Fire/Ice and 3 Terminates for early removal, which are tempo neutral in regard to the typical 2/2 for 2 bear, and can gain Tempo vs. anything costing more than 2 instead of the 3 mana break-even point for Repulse.
There are no Urza's Rages in this deck. The reason is simple: Rage costs three mana, and in this format, it is mostly used to fry some bear. When you pay three mana to destroy something costing two, all that happens is you lose tempo.
My final advice for people trying to win in IBC is to start looking more closely at spells which cost only one or two mana, things like Fire/Ice and Terminate, and less at things which cost three like Repulse and Urza's Rage, so your deck can gain a nice tempo advantage.