When I lived in Cleveland, I came here about six or seven times. From what I remember, admission is free, but they charge for special exhibits. The permanent collection is pretty extensive for the size of the museum, and I never got bored of the place even though I came pretty often.
Overall, as a museum, it's a solid four stars. But it gets an additional fifth star because it's surrounded by a beautiful area that's fun to walk in and because it's free. Yes, I know, donations are appreciated, but I was a volunteer at the time, and free entertainment kept me sane.