270.xx (including release) GTX460M on my Asus G73JW (2.6.38 and 2.6.39-git)
FPS in compiz or kwin is 2x slower.
No composite same, 2x slower.
Scrolling in Firefox (v4) is lagging, slow or simply hangs for a sec or two.
Using Gentoo, reverting to 260 fixes all.
Profile is always on performance.
Option "RegistryDwords" "PowerMizerEnable=0x0; PerfLevelSrc=0x0000; PowerMizerDefault=0x1; PowerMizerDefaultAC=0x1"
Using vsync or not makes no difference.