Saw your question and decided to load up NV again. I'm running this on the ATI 6750 GPU with the 2.2 Sandy Bridge. The game auto-detected my settings and set it at high, with AA at 4 and AF at 8, but kept resolution at 1280x800. I changed it to native 1440x900. In the game, I played with the actor/item/object fade distances I moved them on full distance. I also changed the distance for the other default items that were less than half to half. There can be a bit of a stutter when traveling through the world with the distances extended so far. I may play with my settings the next time I decide to actually play through another character.
Moving around in Novac with the doctor, the mercs, and the brahmin in view, I was getting between 45-60 fps (v-sync is on so 60 would be my max). Then I decided to start launching grenades at people, figuring the explosions would cause some dips and sure enough, they did. Lowest dip in fps I saw was down to 35 fps.
Running around slicing the NCR troopers at Camp Golf really showed a slowdown. Between the building, tents, and surrounding troopers and rangers the GPU showed slowing like it does when launching a bunch of grenades. Most of the time fps floated between 35-45 during action moments and even went as low as 30.
Killing everyone at the 188 Trading post with just guns showed better performance. I don't think fps dropped below 50 and most of the time when I looked, it was at 60. Hope this helps.
