My husband would agree with Debi - the marsh and the tides were his favorites. He said he could happily sit on the porch all day long and watch the tide go in and out of the marsh. With an 8-foot difference, it really was pretty amazing.
My personal favorite was the flat bike riding and great bike paths. Living in hilly NH with no bike paths, it was a great change to be able to ride without getting seriously winded, and to ride safely most of the time. Since our 6yo is still pretty tentative on a 2-wheeler, this was particularly important to us this year.
I also wanted to mention that I just loved the attitude of the CM's, from the social directors to the housekeepers. Everyone really had that "Disney difference" that I had come to expect at Disneyworld but wasn't sure would be here. I was so impressed that everyone always said hi to us and that one time when we were doing Tommy's treasure hunt, one of the CM's stopped to ask if we needed help with anything (I guess we looked a little lost).
Needless to say, we're adding on as soon as the paperwork comes through.