I thought it might be helpful to put up links to copies of my current fallout.ini and fallout_prefs.ini. I've modified these to make New Vegas as stable as I possibly can so nothing is pushed too far beyond reasonable limits. I've optimized settings for lighting and LOD which have a minimal impact on performance and have included all recommended multithreading changes and a few tweaks of my own. These are also set up for DarnifiedUI so if you don't use Darns then restore the defaults by replacing the lines under [Fonts] with those starting with a semi-colon (;).
I don't recommend copying and pasting these. Use them as a reference for making modifications to your own existing files which are found in Documents > My Games > FalloutNV. My PC is getting pretty old now with a Q6600, 8GB ram and a 6850 1GB so if you have plenty of headroom by all means change settings to take advantage of newer hardware. One word of caution is to leave uGridstoload = 5 alone. Yes you can make your game much nicer looking by increasing it to 7 however it will just put more strain on the engine and eventually lead to crashes.