Well I just did some really quick before-and-after benchmarks to see if the 177.40's did anything for me compared to the 175.19's. I was disappointed to see that it actually lowered my 3dMark06 score by a small amount and it did nothing for me in Crysis. I checked to see if Physx was an option but it was greyed out for me, and I included a screenshot of that as well. Hopefully this will help some people out and maybe save you all some time.
Oh and all the benchmarks were run on the "rig" that's in my signature. I'm going to leave the 177.40's installed and play some GRID for a while and see if I notice anything different. I don't play with the FPS showing so unless there's a noticeable "seat of pants" increase in performance I'll probably switch back to the 175.19's.
EDIT: Here's a breakdown of the benchmarks incase you don't want to D/L my screenshots:
3dMark06 (Default @ 1280x1024): 12,380
Crysis (All "High" @ 1680x1050): 37.86 avg FPS
3dMark06 (Default @ 1280x1024): 12,342
Crysis (All "High" @ 1680x1050): 37.75 avg FPSEdited by Gash05 - 6/26/08 at 3:29pm