So, I completely recommend a stop by the R&R HOF if you're in Cleveland. My 3 star review isn't meant to discourage that, just to maybe temper some expectations. As my wife said as we exited, it was "okay". I perhaps liked it quite a bit more than her and the reasons for that will help you decide if you would like to attend or make a trip especially for it.
If you're a fan of popular music in general with an emphasis on rock and roll, particularly early rock and roll and the seeds of inspiration for it, you'll really dig the Hall of Fame. If you're a super fan of a few particular artists (as my wife is) you may be disappointed to see some things lacking--for example, she loves Dylan, the Band, Van Morrison and the Beatles in particular and aside from the Beatles she didn't see much from those others even though they're in the Hall (you can't force an artist to donate something afterall). And as a Beatles fan she didn't see anything particularly new or exciting though she enjoyed what she did see. I found a lot of really cool things to look at and we both really enjoyed the full concert experience video (make sure not to skip that on on the 3rd floor).
So, it's really worth a visit particularly if you love rock. If you've devoured rock biographies like we have you won't find any "new" information from any exhibit but seeing Hendrix guitars, original penned lyrics, Prince outfits, and a slew of other artificacts is totally worth it and cool. Just don't build your expectations up to an unreasonable level beforehand!
Note---save $2 if you buy your ticket ahead of time (the day before). Parking isn't included--there's a nearby (10 minute walk) garage you can get for $11 or so with a $2 discount if you get your ticket validated at the Hall of Fame. There's a nearby riverside park worth checking out and downtown dining is within a walk as well. Crowds--we went on a sunny Friday and it was packed. Our Cleveland friend mentioned a lot of folks make it a 3 day weekend in Cleveland so you may fair better on a Wednesday or so--and exhibits like the Elvis one are camped out with boomers!