Menzel's last show is this Sunday. Apparently she hasn't been stage-dooring at all for some time. I'd expect the crowds to be much more manageable when Burns replaces her. Rapp returns to the tour this Sunday.
As for whether or not you'll like the show, check the music and read a brief synopsis. One thing I realized later is that this is a concept musical, but some review it as a traditional book musical, which it's not.
I loved the show. I think that it's definitely worth seeing.
Rapp was very nice at the stage door - I got to chat with him for a minute and he signed my copy of his memoir. He didn't take pictures, but I saw the show in late December (2014) so he was probably trying to spare himself from getting sick. Very pleasant man, and a wonderful performer.