Well, in 1999 we stayed at the Poly because my DD was 4 and we wanted the convenience of a monorail. It was great! We spent most of the time in either MK or Epcot, so being able to get back for rest time in the afternoon was great.
In 2003 we stayed at WL for the theme. I had planned to stay at CBR, but WL is so beautifully themed, that it lured me away. It was great. There's no monorail, but riding on the boats was great fun and very quick. Also, being able to watch the nightly water parade both here and at the Poly were great.
This year -- in just 8 days! -- we're staying at AKL. Again, it's the theme that lures me. I wanted to stay here in 2003, but DD, then 8, wanted WL. Now that she's 12, she's very excited about AKL, as we all are. I've heard the detail there is incredible. I can't wait!