I went on the Monsters of Rock cruise in March. I would say it was a good cruise for my first time, but I would definitely cruise with a different line next time.
The pros:
-Service was great. I never found anyone to be less than helpful and courteous.
Nice balcony, lots of storage, quiet room. Seems like a very long walk to the cabin, until you figure out there's an elevator behind a small maze of hallways.