I sailed on HAL after sailing RSSC. I did have a good time but I felt that if I hadn't upgraded to a full suite, I would have been disappointed. I was on a similar ship, the Oosterdam. The full suites (but not mini-suites) get some extra perks which make the experience similar to a RSSC cruise (welcome champagne, access to the Neptune lounge, better cabin ammenities, a private suite cocktail party and lunch). My biggest letdown from RSSC to HAL was the food/dining. I really don't like set dining times and I feel the food has dropped in quality and really doesn't compare with RSSC. However, the specialty restaurant was excellent but it does carry a surcharge ($20 I believe).

It's a different experience, and if you go into it with a positive attitude, I think you'll have a good time.