A few disclaimers:
1. I came to the Rock and Roll Hall of Fame during a corporate event - it was free to enter.
2. I'm not that "in" to Rock and Roll/music in general.
That being said - the museum is Fine. There is lots to see (mostly costumes and other paraphernalia) and little to do. There are a few films about the influence Rock and Roll had on the nation/world which was pretty interesting.
I think the part that I enjoyed the most was the architecture of the building. It reminds me a lot of the Seattle Public Library. The building itself it just cool. It sits on the shores of Lake Erie and gives off some remarkable views. As you walk into the museum, there are hundreds of guitars that were designed my artists - each with their own unique take on the shape - very cool!
I wouldn't go back and I probably wouldn't have paid to go in myself - but it was fun to go.