I've been in here twice in the past, but never paid the entry fee to see the entire exhibit. This time I did, and I must say I enjoyed my time there although I'm not an avid music fan.
While the exhibits are moderately entertaining, the highlight is the building itself, designed by I.M.Pei it is absolutely beautiful. As you ascend, each floor necessarily becomes smaller and has less to offer, but the view is marvelous.
Think a little Louvre. Very cool.
A fun time.