I really like Westfall. It isn't glamorous, there aren't a lot of notable sights (unless you count the battle ship in the Deadmines) and it doesn't exactly feature amazingly cool landscapes. However, there is something about that place. I know the quests, I can do them quickly, and once you snag Van Cleef's head, you know it is time to hit the road.
The opposite of the comfort I feel in Westfall is Stranglethorn Vale. Most especially on a PVP server. As Alliance, STV on a PVE server is simply annoying, with the lack of a Northern flight point making the running a little over the top. On a PVP server? You get ganked. You get ganked again. If you dare call for reinforcements, good luck to you, as Grom'Gol village is in the neighborhood to shuttle in Horde by the blimp load. And if you don't like the ganking in STV, you can always go to Desolace, which might be the ugliest zone in the whole game. In addition to being ugly, Desolace comes complete with spread out quests and long, long runs. So I guess Desolace and STV tie for my least favorite.
What about you guys? Do you avoid any one zone in the game? Is there one you always look forward to?