I bought the game today, I'm two hours in and so far zero crashes/freezes and no bugs whatsoever except for some type of "bright white" flashing texture issue, though I see from this thread I'm not the only one getting it. I haven't updated my drivers though so I bet that's it.
For fun while I was waiting for Steam to d/l New Vegas (small d/l btw - under 5GB's) I launched a new game of Fallout 3 starting right when you walk out of the Vault for the first time. The game completely locked up on me twice in the first 10 minutes, and I will say that FO3 was NEVER a stable game in my experience (and I played it a lot and on two different hardware configs - one AMD and one Intel).
I will say a couple things about New Vegas - the flashing textures are annoying, I need these fixed.

Being able to aim down the sights is very nice and an appreciated addition, but the gunplay is still sub-par for an FPS - it remains "Oblivion with guns" - or in other words not a good shooter. Battles are still clumsy and there's still the "invisible dice rolls" going on every time you shoot. This is fine and it worked great in Borderlands but man oh man does New Vegas (and the Gamebryo engine) feel like old trash compared to Borderlands.
The voiceacting has been okay so far but I'm skipping a ton of the dialogue already - not a good sign at all in terms of immersion. Right now I think I'm gonna focus on the main quest and then after beating the game I'll go back into the wasteland and explore a little and do the many side quests available.
But overall I think the game is fine so far, I'd have been happier with a $39.99 price tag but so far it's been fun and I'm not hating it like I'd feared...etc. Let's face it, if you're a fan of open world games then you are probably gonna like this game even if it's so familiar to FO3 and burdened with terrible graphics.