266.58 WHQL out. For 400 series as well.
FWIW my WEI for graphics went up from 7.2 to 7.3 (GTS 450) but my Peacekeeper graphics scores (2D accelerated with Firefox pre beta10) seem to have gone down some. I am getting nightly Firefox beta builds - though I don;t think I got one between Peacekeeper runs, I could have. That is all I had time to do for now.
EDIT - my Peacekeeper score, after running again, is about the same as the 260.99. So 2D acceleration is about the same.