Since you said you went to Disney theme parks solo before, I assume that you don't mind (or enjoy) seeing kids, and the who "Disney Experience". If that's the case, then I think you'd enjoy the cruise. We went as a family this past April, and while almost all of the people there appeared to be travelling with someone, there were plenty of activities where people split up when not everyone was interested in it.
If you're wanting to party with other singles in the bar until 3am, it's not a smart choice. But if you want a classy atmosphere with that "Disney Magic", and you get a kick out of seeing Mickey Mouse, and watching the faces of the kids, then you'll have a great time.