There has been lots of patching for NV. It went from game freezes every 2 hours to game freezes every 10 hours for me hahaha. So yeah, it's not perfect, but it's a lot more stable than it was when it was reviewed and hasn't bothered me since the patches.
Gameplay-wise, I <3 NV. It fixed a lot of the problems I had with FO3, like removing the nigh-invincibility gained from being in VATS, though I guess if you haven't played FO3 you wouldn't know. But gameplay is better. Story and characters are also better, IMO, and some claim the feel of FO3 from the environment is better, but I think it's just as good (different, but good).
Idk about the DLCs yet... I just made a new character who I'm going to level to 30 and then buy the DLCs.