I've been doing a fair bit of traveling recently, and had been having problems getting wireless networking to work in certain hotels. It would connect just fine, but would stay "local only" with no working DNS.
Some searching around came up with a solution here. It seems Vista is trying to be too smart, and has problems with some older routers. I implemented all three fixes listed. Although I'm guessing only one of them was probably necessary, I've been too lazy to investigate further.
Another welcome side-effect I've noticed is that it seems to negotiate a wireless connection faster than it did before.