I looked at the Trip Adviser remarks, and their scores are pretty good. I also noticed this must be a pretty new tour since the remarks didn't start until January. I also noticed that a LOT of the remarks are from people that live in Nassau, so I'd discount those, they are probably from the people who would profit from the tour.
I don't know if I'd try it, until they are more established...I think that the front street of Nassau is nasty, and I wouldn't want to spend the rest of my cruise in the bathroom.