So I finished my third and fourth playthrough of Fallout New Vegas yesterday. To be fair I didn't start a fourth game and finish it, I just continued from a save that I made about half way through my third playthrough and went from there. I started with the NCR, did the Legion next and saved the neutral endings for last.
Overall I am very satisfied with Fallout New Vegas, the addition of factions really adds a nice dynamic to the game that Fallout 3 did not have. I was underwhelmed by the crafting in the game though, both for ammo and survival and the random crashes to desktop and occasional buggy-ness of the game was sometimes off putting. But I would highly recommend Fallout New Vegas to anyone who liked Fallout 3, it's worth it.