Playing the game was unbearable, random freezes even when there was no NPC's around and random hangs, when talking to a NPC the frame rates would sink, my system is fairly decent so naturally I was pissed off.

I tried almost all fixes but that did not work, until of course I stumbled upon the d3d9.dll fix, after applying the simple fix, the game runs PERFECTLY. Barely any noticeable lag.

Hope this helps somebody else
http://segmentnext.com/2010/10/19/fallout-new-vegas-errors-crashes-freezes-fixes/
(See no 14)

do note that this will not work if you have two monitors, disable one monitor

Same sees to go with multi-GPUs. I get higher FPS using one core of my 5970 instead of both. Enabling CrossFire with the DLL makes the stuttering even worse than without the DLL file. Alas, I just have to disable CFX every time I play the game; hopefully this is patched up soon enough.