Guys, you need to rid yourselves of this multi-GPU hate. Things have come a long way since the 7950GX2.
What was that, like 3 years ago?
I can't speak for SLI this gen, but Crossfire has been perfect in just about every game I have tried thus far. Even with 4 GPUs I get no more lag than I do on a single card. And just about every game I have tried has scaled in a big way. I've tried around 20-25 different titles, and the only two that haven't scaled at all were Two Worlds and Witcher. Witcher ran at 75fps average on a single GPU already, and Two Worlds, well, .. that game just sucks.