I'm getting highly fluctuating framerates in UT3 which is strange because its running on the decently powerful 8800 gts 320 MB. I'm running it on 1680x1050 with max settings, which ran perfectly under XP but runs like crap on Vista Ultimate x64.
Intel Core 2 Duo e4400 @ Stock (2.0 Ghz)
MSI 650i SLI
NVIDIA GeForce 8800 GTS 320MB
2 GB DDR2 800 Mhz RAM
Windows Vista Ultimate x64