It's alittle buggy at launch, but almost all of Bethesda's games are. The changes and tweeks that Obsidian have added made the game that much more fun. Skill magazines are now added for a quick boost to your skills in key situations, a command wheel for directing your various companions that you'll meet and ironsights for almost all the guns for that fresh out of Modern Warfare feel. The additions to the game are small, but add depth to an already deep game.
While I haven't made it to New Vegas yet, the Wasteland is full of new mutated animals and other things that make life in post-apocalyptic America difficult. Nothing like getting your ass handed to you by a mutant butterfly to humble you quick. I haven't even found the two headed, mutant bears yet. That's looking like it's going to be a fun time when it happens.
The factions are more realistic, where no one is really the "good guy", just groups of people that are out for self. It's more real. Rather than the "right" thing and the "wrong" thing to do, there are choices to make that could be the right thing to do at the time, but could have consequences later in the game. I like that part alot. It makes what you do more realistic. If you help a faction in the game, another faction is going to not like you as much and you'll be banned and attacked if you cross the faction out in the Wasteland or if you wander into a territory controlled by them. Worrying about whether or not you'll get shot at on sight. It's little additions like that that make the game for me.
Anyway, it would take too long to go into everything that is in the game. It's a huge undertaking. And in a world where other companies want make gaming a "simpler" experience, I'm glad there are games like this still getting made for me to lose huge chunks of my life playing.
And having a machine gun that shoots hand grenades isn't bad either......