I've only played about 5 minutes of Crysis so I can't offer an opinion on the game as to whether DX10 adds any benefit, but I have played Halo 2 for PC and quite frankly I think they can keep DX10. I see no difference to the graphics. The load times are longer and the HDD seems to spin continuously.

My PC isn't a CPU crunching, bone crushing behemoth that eats frame-rates for breakfast, but it's no slouch either. I expected more from DX10.