I see the GTX295 blowing the 4850x2 away, unless running really low resolutions,
It's a demon
Low resolutions are useless for dual-GPU cards... there will just be no differences in performance, even with AA, as far as I'm concerned. High AA seems to depend more on memory, not raw GPU power, so at low resolutions, fast dual-GPU cards can compare to mid-range single-GPU cards, depending on the title.
The GTX 295 is a unique breed though, and it belongs to the 30" club. You have no reason to own that card if you don't have a 30" monitor, it's that simple. The GTX 285 on the other hand, is uber-fast and will benefit anyone, thanks to it's faster clock speed. But even then, a 24" monitor minimum is recommended.
Seems extreme, but the good news to gleam from this is that all these findings mean is that affordable cards offer enough power for most people. That's a great thing.