It is supported, but for whatever reason the profiler app doesn't tell you if they're enabled or not.

What I found is that the quickest way to check if CI/QE is enabled is to start DVDPlayer.app. It will give an error about not finding a supported display device if CI/QE is disabled.

As for the fix, I have found NVEnabler to be the most consistent way to get my nVidia card to work properly. EFI strings seem to be hit and miss in SL for some reason.