I was following this post a couple weeks ago and felt everyone had the pro's and con's covered pretty well. I didn't think I had anything much to add. I was re-reading tonight and came up with a point.
Another valuable benefit of slide-toppers. Decreased solar heat load.
The slide walls, floors, and ceiling have a lower R-Value than the rest of the roof and walls. Slide toppers provide shade over those roofs. I guess-timate that our 3670 has about 72 square feet of slide roof. That's almost 20% of the total roof square footage.
In the hot Florida sun, that can equate to a lot of A/C runtime.