Overall we had a great experience. The room was immaculate and well-appointed. The staff were friendly. The food on-site was great. There were many activities available to us, although we couldn't take advantage of all of them because of our short time there.
Our only fault would be that some of the staff were obviously inexperienced and maybe lacked some basic operational knowledge -- this is probably because they are young, seasonal staff and just need more training. For instance, asking basic questions and having to wait for a more senior staff member to clarify or correct them before getting the appropriate answer.
We also used a babysitter obtained through the hotel and we were quite pleased.
All said, we would likely return in the future. We enjoyed the Winnetu and its proximity to Edgartown.