Still trying to find a better video OC program? Try Powerstrip.
http://www.entechtaiwan.com/
It is the only program that I have found that does exactly what I want. It allows me to OC my Core and memory clocks and adjust the gamma settings while playing a game; no ALT-TABing necessary. Also has LOTS of cool tweaks you can use as well; enabling anti-aliasing and anisotropic, disabling v-sync in both D3D and OpenGL, and lots more.
On my GF3, the program allows up to 266Mhz core and 609 memory OC. Of course I cant say what it will allow with other cards but the compatability list pretty much covers everything and supports all MS OSs.
Try it, cant hurt..........Unless you fry your video from too much OCing
Good luck.