We were on Louis Cruise lines last summer on the Calypso. We were with a tour group and had originally been scheduled with Royal Olympic before they went bankrupt.
The ships are small compared to the superliners of the Caribbean, but we were comfortable. Don't expect the quality of the first-class cruise companies. Louis has a number of ships the follow approximately the same itinerary and there were usually 2-4 of their ships in the ports simultaneously.
Cruising in the Greek islands was beautiful because you are almost always in sight of at least one island. The seas were calm when we cruised. Our cabin was small (of course, most ships have small cabins), but had a nice window. We usually spend most of our time out on the deck or involved in some of the ships activities so are not in the cabin very much. We had a great time!