I just got an iPad 3G (thanks, work!) but I'm a little reluctant to rely on it at Disney because I like to be able to upload photos and videos while I'm there and I'm afraid I'd go over the 2GB for the monthly 3G plan. I'm still thinking about it, though. (I got the SD card adapter to upload photos, so maybe I'll just save pictures to the iPad and wait to upload them until I get home.
Decisions, decisions...
That said, I've only had trouble connecting with Airport Express one time but I reset it and then had no trouble at all. Last time I was there I took reset instructions and setup instructions and taped them to the inside of one of my Owner's Locker lids. I can't find the files I used though - I must have done it on DH's computer.