Where have there been reports of DX10-lagging with current 8800GTX cards? I am not a GPU guy per-se, so I am a bit out of the loop. The only DX10 game I've tried was Lost Planet, but I didn't delve too much into it because the game is one of the worst I've ever loaded up. Boring and needlessly laggy, even in DX9 mode. I still stand by my thoughts. DX10 is on the way, but it's not going to be 'commonplace' by years end. I'd be skeptical to see dual 8800GTX have a hard time with the new games, but I could be wrong.
As it stands right now, I can run most games at 2560x1600 max settings with an 8800GTX. I couldn't imagine the power with two. Lost Planet lags a bit, but I blame that more on it being a weak port. If it was written fresh for the PC things might be different. I'll need to perform tests within the next month and come up with my own conclusions.