I watched an episode of "Mighty Cruise Ships" that showed the Europa 2. It sailed from Istanbul. About 500 guests, $6,000 pp. Every room is a balcony suite. Anyway, the passengers voted on where the ship went. There were two votes during the 10-day cruise. Even the captain doesn't know where they will go until after the vote. Once the vote is decided, the excursions crew scramble to figure out excursions.
Would you go on a Surprise Cruise?
I don't think I'd like it. I like to know where I'm going. Plus, since excursions were last minute, I think better ones could be arranged if they had prior knowledge.
The guests seemed pretty happy and of course, they wouldn't have gone on the cruise if they weren't okay with it.