Using final. I've not used FF4 betas.
Guess we need to find more people with NVIDIA cards to chime in.
1/1 on GTX460.
By the way, I've figured out a bit more about the AMD/FF4 bug. Exploring identical sites on IE9 and FF4, simply clicking on links and scrolling would shoot clocks/voltages to 3D on FF4, whereas it would only hit "blu-ray" clocks/voltages on IE9. Also, as I've noted before, after browing for a while in FF4, the clocks will just get stuck at 3D levels and will require a reboot to get them down again.
Edit: On my Nvidia system, the card's clocks react differently than on the Radeon system. It seems that the card is less likely to hit full 3D clocks while browing in either browser, but when it does, it stays there much longer, on the order of 10 seconds, while the Radeon cycles back down more quickly. Also, as for IE9 vs. FF4 on Nvidia, it appears that FF4 does trigger more ramping up of clocks, but not to the same degree as on the Radeon, and it's certainly never become stuck at 3D clocks on my Nvidia system.