I really like the Senses spa at the Grand Floridian. They offer different types of manicure and pedicure. When I went in December, Dee (I think that's her name) was the one who did my manicure and she was great!
I also vote for Senses. Went in January and really enjoyed the experience. We used to go to Mandera Spa at the Dolphin resort and sadly they aren't as good as they used to be. We'll be going back to Senses again in October maybe even the new one at SSR.
I think we made our reservations a week before and had no problems getting the day and time we wanted.