I've done the Prince of Fundy cruise (on the Scotia Prince out of Portland, Maine) at least a dozen times. I would be happy to answer any questions you may have; please feel free to e-mail me at email@example.com
For the sake of comparison, I have done nine "real" cruises, most on Carnival, a couple on Disney. I say "real" because you just can't compare the Scotia Prince, or it's sister ship, Bluenose, to a "real" cruise.
The Prince of Fundy cruises are a blast. We love them (obviously.) But if you are expecting something comparable to a "real" cruise, you will be disappointed.
The Scotia Prince is far smaller than "real" cruise ships. The public areas are not extensive. Most of the cabins do not have private baths.
But on the up side - it is a great time at a very reasonable price. There is show on both the day cruise and the night cruise; the shows are always fun and upbeat. There is a nice casino, little shop and a few dining options. The main dining room is serves buffets at breakfast and dinner, menu options at lunch. None of it is anything to write home about.
We found Yarmouth, Nova Scotia beautiful, but cold with little to do besides sight-seeing. If you are into scenic coastlines, it is paradise.
Again, please feel free to e-mail me if I can offer any more information.