Yub Nub is a terrible song. It really completely devalues the somber but hopeful ending of ROTJ for me. It's way too campy. Maybe it would work in another situation, but the SE music is far superior for conveying a bittersweet victory with a lot of work ahead for the Rebels.

Generally, the best changes in the SE are ones you don't really notice as much. Cleanup work and the like. I also liked the dewbacks and such, though they were too noisy (LOOK OVER HERE I'M NEW). The droids and rontos were too much. The lead-in to the cantina wasn't bad. I liked most of the stuff in ESB. Cloud City really lends itself to the more open style, though it was sometimes subconsciously distracting (which is my general complaint for most of the SE changes).

I honestly can't remember many of the ROTJ ones off the top of my head.