The issues concerning ATi video cards has been solved in the beta patch. However, there are still problems with quad core PC's Google for it, or check the readme file for the 1.03 beta patch to find a workaround.
I played the whole game through with no issues on my quad core 6600
Q6600 @ 3.2GHZ
4GB Corsair Dominator @ 1066MHZ
GTX280 1GB
Samsung Spinpoint F1 1TB (Win 7 Pro x64)
Seagate Barracuda 500Gb (Win Vista Ultimate x64)
Antec 1200
Corsair TX650
Creative Gigaworks 2.1
26" Samsung T260 LCD