running in 32 bit mode (still vista 64) improved the fps to 120 from 30-60 on the lost coast benchmark.. still less than expected but i'll run some other tests as this seems to be at least partially a hl2 64bit problem for me
I wouldn't put too much faith in the new driver release, although I wish you the best of luck. Just so you know you aren't alone out there:
I've been having similar problems on my Gigabyte 4870. FPS in Half-Life 2/TF2 range from 20 to 60, in game... at 1280 by 1024 (!!) .. AA settings don't...