Good review Jimbo.
Looking at it.. If you have a GX2 it can't be worth switching.
Fact is yes it will give off less heat and be quieter and have the stability of a single GPU but if none of those bother you then you're getting roughly the same FPS at a slightly lower price.
However, with the results being so close and the 280 actually beating the GX2 in a few of the benches, I should think with a driver upgrade or two it may well overtake the GX2 in a few of them and extend its lead in the others.
Technically it is new architecture so it's probably not just a case of updating and tweaking the drivers like they may have been able to do with say, the 9800GTX. I think my point is that there may be higher yields from a driver update than with the previous generation.
Yeah.. That's what I mean