they are not problems... it's just that the resulting quality of the game rendering is poor compared to Ati's
it's very dissapointing since i've upgraded to a SLI 8800gts and although the fps boost is awesome... the Ati render seems more natural and blended...
if you see the picture i posted in the post that i pointed out in the guide post, in the horizon, there are yellow lines that are caused by texture overlapping in the zones that have shadows over the track. It's not very noticeable, but they are annoying if you are not used to them. have a try... play a few laps over blackwood in the fox, and watch out for the shadows far in the horizon, you'll see that there are yellow lines around shadows when there are far away... it's very slight but come to think of it.. why there are lines that are not black, green or grey... shadows don't have yellow, yet you are seeing yellow lines in the track.
again, it's not a problem with the game nor it is with the video board.. most people won't notice them.. but when you have time playing with the ATI that doesn't have this things, switching to the nvidia then makes you feel that something is not right.