We took the Passport to Central America cruise in May, 2008 on the MV Explorer. This was an enrichment voyage run by the Institute for Shipboard Education (Semester at Sea). We have taken many cruises from Carnival and MSC.
The voyage embarked out of Nassau, Bahamas. The port is very disorganized, hot, and the taxis are expensive. The crew and staff on the ship are also disorganized. They try to take part of their regular staff and create shorter cruises to fill in between their regular semester cruises. The disorganization really shows.
The ship is OK for a small cruise ship. The library and internet access are probably the best things on board. Cabins seem to be regular size, but the beds are the worst we have encountered.