Well, Sheik is back in but I think that was sort of expected. What I find interesting is that he has his own Final Smash, which could be interesting in what it does differently from Zelda's.
Also, after spending the last half hour listening to all of the music samples again I just want to reiterate that this game has an absolutely stunning soundtrack. Not only does it have incredible nostalgic value but all of the arrangements are absolutely impeccably composed. It's hardly surprising given the amount of musical talent that Sakurai roped in, but I love it to death anyway.