I just flashed my GT to Ultra, and it'll now do 420/1200 (used to be 410/1180), and gave me an extra 100 points in 3DMark03, along with tighter RAM timings. No huge increase of any kind, just kind of a cool thing to do. I would definatly not do this if you aren't comfortable with it, because it is kind of easy to screw up or get confused. Thanks to this guide : http://www.ocforums.com/showthread.php?t=314079 for instructions and the BIOS.
*I am not responsible for any damage caused to your computer by flashing a card's BIOS.
*I am not responsible for any damage caused to your computer by flashing a card's BIOS.