OK, just had a quick play after extracting everything Nvidia out of the iMac update (including AppleGPUPowerManagement) and it doesn't appear to have made a difference. I think the drivers I got from Nvidia fixed the mess that 10.6.4 made but they are apparently specific to the GTX 285.
I was playing WoW prior to the update and sadly I can't run it on high or extreme but still get decent detail but FPS drop to ~30 in Dalaran.
I applied those kexts via Pacifist, touched the Extensions folder and restarted and yeah, no different. I also checked the driver version and it says version 2.1 Nvidia 1.6.18. Sadly I don't know what it was prior as I didn't know where to find it at the time.
I have noticed a bit of screen tearing though, this is only when I'm not using any graphics intensive apps. Weird thing is, It doesn't appear when a game is running like if I have WoW in windowed mode and quickly move a window around, it's smooth but if WoW is closed (or any other game) I get the tearing. This was happening before I played around with the drivers.
Would be awesome if I can get Ultra settings in WoW with a constant 60fps
😛
Also, if anyone's wondering. Here's the contents of the driver from Nvidia (19.5.8f03.dmg).
It appears as though that will work with most Nvidia cards although their site said it was specific to GTX 285.