ATI has a kind of RTM driver but Open GL doesn't work on that, while Nvidia has a WHQL driver with OpenGL broken and various Direct 3D bugs in the driver package.
ATI's driver can run 3Dmarks and most of the Direct 3D games, which implies that ATI is a bit more ready with its Direct3D drivers. Nvidia's Open GL driver is in better shape but still not even close to the one for Windows XP.
There are only three days left before you will find Windows Vista preinstalled on machines and laptops so we reckon that there should be a non public Vista driver version.
Nvidia's driver still doesn't support G80 cards or SLI - the two key marchitectures at the moment. ATI demonstrated Crossfire Vista support but it still didn't include it in driver, yet.
You can bet that both driver teams are working round to clock to prepare the final RTM drivers and we expect the update by the end of the week.
The real Vista for retail/etail customers comes out on January the 30th next year. ยต