Performance was excellent here, everything maxed out (Ultra), 1280x1024, 16AF, 4AA, no matter what cars, tracks or view (love ****pit/helmet view!), felt like solid 60fps to me (XP, 158.27).
I did have some sound issues, some sound channel volumes (5.1, actual engine sound and voice channel) were messed up both in OpenAL and DirectSound (highest settings, no fps impact that I noticed, latest XFi drivers, full audio acceleration).
More annoying was the fact that everytime I exit the game the dirt.exe caused the standard windows error/crash message. While it didnīt obviously affect gameplay or game stability, I still find it odd that the .exe crashed like that at the exit. Another annoyance was that everytime I wanted to play and was not connected to the internet the game profiles got corrupted after quitting/restarting the game. When I was online, this did not happen.
Overall I really like this game, it does not have the gameplay and physics of RBR but the graphics and cars alone make this one worth the purchase.