One thing that you might look into is the fiberglass insert tubs. These are made to fit specific tubs and effectively become a new surface. I know that I liked the feel of fiberglass, and its cleanliness potential, but was not wild about the unsupported feel that a regular fiberglass tub has. Haven't tried it myself, but I think that I would be real happy with the feel of the fiberglass and the support of the old tub under that.