I've put over 25 hours into the game (PC) so far, and I've been taking my time statting up and exploring a lot of stuff (just got to novac at 24 hour mark)
I'm using a higher end PC with a GTS250 vid card, and haven't seen any water bugs or nvidia related problems.
I have not had a single crash of any kind or any lockups.
So far, I've only had a couple of small clipping bugs where I got stuck in the side of a steep hill while jumping/falling.
I had one odd quest/NPC oddity, but I'm not sure it was a "bug":
I'm not sure how it's supposed to go down, but when I went to meet "victor" in the first hour or so of play, I found him laying on the hill 'dead' just below the goodsprings graveyard, next to an angry bark scorpion.
Around hour 5-6 or so, I was up in the hills east of the good springs source, plinking coyotes and geckos for the hell of it, and suddenly I look behind me and Victor is alive and well, trying to roll up the hill in the middle of the wasteland and attempting to engage me in the dialogue that I assume I missed before.
I assumed at the time that this was just weirdness related to him being some sort of unkillable quest character ala FO3, and that he'd run afoul of the aforementioned scorpion when I engaged it in combat from afar.
All told, I was expecting this game to rattle it's own bolts out while running, and I've been pleasantly surprised that it's been so stable.
I don't think I've found a truly "broken" quest yet.