I haven't used DriverCleaner yet, but I do have the zip for version 1.5 in my download folder to try when I replace ATI Cat 3.2 with Cat 3.4.
I'd suggest additional checks after using driverCleaner to remove your Nvidia drivers. Check for leftover files by searching for leftover nv* files. Use RegCleaner to check the registry for leftover Nvidia entries.
DriverCleaner looks promising, and many people suggest its use, but I haven't seen a post by anyone who's actually used it.
Hope this helps!