I hit lvl six yesterday and stopped playing when I got to Novac.
As fun as the game play is the bugs or glitches really break immersion. Was heading to novac and had just passed a traveling merchant when 4 Legion dudes started shooting at them(the caravan) I joined in killing the legionares. Walked a little while further and there was about 5 NCR troops, one of which was half buried in the road. The rest looked like they all jumped ont he same transported pad in Star Trek and now accupied the same space. Yes it wasn't game breaking but it takes you of of the world.
Still enjoying Hardcore Mode on Hard. In F3 the Rad Scorpions where a push over, now I have to really plan my attack (and retreat). Fav gun is my cowboy repeater although I dont have alot of ammo for it, my vermite (spelling) rifle is second. Also enjoy the new sneaking mechanics. In F3 i could never go the rouge route. Now if i see some powder gangers I get a close as possible (without being seen) and head shot them.
The only other thing that bothers me is that the lines between good and bad is too black and white. Maybe it gets better later on.
Oh and I miss my gun nut perk.