Today NVIDIA posted their Beta version 185.81 driver. This driver supports GeForce 8M, 9M, 100M, and 200M-series notebook GPUs.
View the release notes HERE.
I have updated the 32/64 bit Vista Driver Pages as well.
With SLI enabled, PowerMizer does in fact downclock the GPUs based on load. I expected this since as of 185.66 NVIDIA seems to have worked this bug out.
Of note, while running the installer, Windows states the driver is not digitally signed. This was unexpected as NVIDIA and most only released signed drivers - no big deal though, just accept the warning and continue with driver install.
PhysX is a bit hosed with this installer (known issue) - IF you have an AGEIA card installed you will need to download and run the installer for 9.09.0408 (http://www.nvidia.com/object/physx_9.09.0408_whql.html). By default the 185.81 installer installs 9.09.0203. Once you download 9.09.0408 run the installer - it will uninstall the 9.09.0203 version. Rerun the 9.09.0408 installer to update PhysX. DO NOT UNINSTALL PHYSX via the Control Panel. If you do you will need to start all over and run the 8.09.04 installer (http://www.nvidia.com/object/physx_8.09.04_whql.html) then the 9.09.0408 installer.
3DMark06 scores are on par with the 185.66/185.68 drivers (actually with 185.81 I initially scored 200 points higher on the first run with PhysX and the AGEIA disabled - 11468 3DMarks). I haven't OC'd the GPUs yet - may do that later to run 3DMark06. As most will agree, in the end 3DMark06 is nothing more than a number - real world performance is what counts.
Left 4 Dead still exhibits the occasional freeze up with sound loop issue - however with 185.81 it is much less frequent. This bug presented itself right after the DLC/Survival Mode update. I don't count this as a hardware/nvidia issue - Valve needs to get on it and figure out what they did.
This driver is a keeper... If you haven't yet, give it a try!