I've heard & read that "CROSSFIRE" is compatible with every game. Were as SLI needs Profiles for each game. Now, since CROSSFIRE isn't really out yet, this is "He said, She said." I'll really believe it when I see it.
But, I think (Dual Card) solutions aren't exactly useless. Yes, you can get by with (1) highend card. But, with games getting more and more demanding, I think it's nice to have (2) cards.
Gamers who want to run:
1.) Highest Screen Resolutions
2.) Highest Game Video Settings
No loss of performance.
Also, with the combination or the soon to be PPU, Higher end CPU and audio 64MB XRAM like X-fi offers... Games will now kneel before you and say, "Your my daddy."
This is all in theory... LOL