In my opinion, improving the duel between Vader ans Obi-Wan was neccessary. not just something fun. The gap between that duel and the great one between Luke and Vader in ESB was just too big. Vader went from looking like a hack swirling a stick to a rather impressive swordsman in just one film. Adywan's edit erases that problem. So I think this partícular change was more than just a fun thing to se.

Of course, there are other things in the dit that are more for fun. Like the buiser batte of Yavin that you mentioned, as well as the extended Death Star introduction.