We just returned from a Greek Island Cruise on the Galilleo and had an incredible time. We highly recommend it. It's a very small ship, there were only 30 passengers this week (it holds more but wasn't full) so a lot of our trip was made wonderful by the other passengers. I don't know that we would have had such a great trip if we hadn't made so many new friends.
The ship is very comfortable. Our cabin on the upper deck was large and the cleaning staff kept it spotless. The restaurant area is free seating, which we liked, and there was plenty of space to hang out in the sun or the shade while sailing (although most of the sailing is overnight). We did have one night of rough seas and the sun deck looked like a bit of an infirmary with sick patients, but the staff handled it really well, handing out dramamine instead of drinks, and we all just kind of sat up there until it was over.
We didn't do any of the excursions and heard mixed reviews from people. The islands are very easy to get around on your own if you do a little research ahead of time. The cruise director was very anxious for us to walk around each town, but we didn't find that nearly as interesting as exploring all the amazing beaches. The one downside of the cruise was that she didn't really customize the experience for the interests of each guests, she really just tried to sell the excursions.
The food on the ship was outstanding. Fresh, delicious, varied, well presented, just great. I could have kept eating like that for weeks on end.
We also really enjoyed the swim stops off the side of the boat.
If you are looking for a small cruise experience, where you get to know your fellow passengers, get to see islands that aren't overloaded with tourists, and maximize your time on land, this is for you. If you're looking for a cruise with a casino, formal nights, etc. . . . it's not for you.
Piraeus is really just a port town. There's not much there. But there are hotels and restaurants ringing the two ports and it's convenient to get to.
Loved it! Take the bus to all the beaches and party!