My wife and I spent a week on the Windstar Sprit cruising from Athens (7/14/2012) to Istanbul (7/21/2012). We had a very good time (A-), but the heat was terrible with the temperature over 100 degrees most days. There are not many online reviews of the Windstar line or this itinerary, so I hope this review helps. We are not "cruise people" and the only other ship we have been on is the Disney Dream with our children.
The Sprit is a motorized sailboat which carries about 140 passengers and 96 crew. It is much smaller than a large ship such as the Disney Dream. On average, the sails provide 20-30% of the propulsion.
The atmosphere is very casual with no formal dinners or theme nights. For dinner, they request men wear slacks and a collared shirt. You can visit the bridge anytime the boat is sailing. The crew members are almost always willing to talk to you and answer questions. The average passenger is about 50 years old and most are married couples ranging in age from 25 to 70. There were a few teenagers and a few friends traveling together. I did not meet any passengers who were traveling alone. During our trip it was 100+ degrees most days and you needed to be somewhat physically fit to tolerate the heat and climb the ruins. The few passengers over 72 y/o struggled at times on some of the tours.