I just picked up a BFG GTX 280 OC for $375 from CompUSA (424 shipped-30 rebate-20 paypal) and sold off my 4850's in Crossfire.
Verdict: I like the GTX 280 much better. Much easier to setup and smooth as silk. The ATI cards in single or dual configuration has always given me jerkiness in 1946. Rolling the airplane always resulted in a slight pause, drove me nuts. This is with both a 3870 and 4850's. I've given it a shot twice with ATI but simply found nVidia to be better, both with an 8800 GTS G92 and now the GTX 280. Currently using beta drivers 177.79.
I didn't buy the GTX 280 just for 1946, it really shines in new games such as UT3 which is outstanding.
All in all both ATI and nVidia are good performers, I just like OpenGL performance of nVidia in 1946 better.
