I have slept on the sofa day beds at the Grand Floridian, Yacht Club, and the Polynesian. I am 32 year old woman who is 5'5". I sleep on a really great bed at home, thus making me a little more particular. The day beds were very comfortable. They are a "real" twin size bed. They were great.
I stayed at Saratoga Springs on a pull out sofa on our last trip. To me, it was very, very uncomfortable- I ended up just sleeping on it like a couch. The "pull-out sofas" and the "day bed sofas" are very different.
Just as a heads-up.