I have been in a Cruise in March 2011, from Rio to Fort Lauderdale, 14 days. I was a little bit preoccupied, as it was my first time with Princess. I have travelled with Royal Caribbean and NCL before.
The ship is nice, with 4 pools and lots of jacuzzis. One of the pools has a glass ceiling, good for raining days. There is also a pool in the back of the ship, so the view is great.
The food was awesome. I opted for the 2nd serving, same time every day. There was always one or two great options in the menu, always great. 3 days with lobster, more then 5 days with shrimp in the pool and/or dinner. Food was available 24/7, as breakfast, evening tea, lunch, dinner, etc. you can also order breakfast to your room, free of charge, so you can have it on the balconi. Fantastic.
The entertainment was good, some shows were very well produced, with lot of scenarios. Not all of them were great, but it is a matter of taste. Some people (and some nationalities), laughs just about anything :) If we didn't like the show, there were at least 2 other entertainment options going on (including a great Brazilian band).
If you don't like to spend to much time inside the ship, it could be a problem. Me and my girlfriend just loved the "at sea" days, as the ship offered a lot of options and the pools were great. In 14 days, we stayed 7 days at sea.
The medium age was high, but it was like that in a 14 day cruise I made with NCL also in Greece.
I recommend Star Princess, and have met a lot of people in the boat that travels a lot with them and like the cruise line.
Princess seems to be a company concerned with their costumers. They talked a lot about the importance of the survey we would receive in our email. They congratulate you on your birthday, serve you a special cake in dinner, sing "happy birthday" and hang balloons in your cabin door. The cruise started with everything in English. After some complains about from the 300 Brazilians on board, they translated the newspaper and put the 2 Brazilian girls in the cast to talk in the TV channel and present some entertainment.