Haven't sailed the Liberty so cannot speak for her but we have done 9 cruises on CCL, 4 on Royal Carribean and 2 on Princess and I can honestly say we have not had a bad cruise. Some better than others. Have noticed the food quality hasn't been the best the past few time but for the most part the service was ok.
The thing that my wife and I look at is that sailing it still the best bang for the buck if you don't have to fly to your port. We have a 5 star time share and we were going to use it this Nov but the air fair was going to be $1900.00 and then we would have to eat out everyday, so figure at least $100.00 per day X 7 days would be an additional $700.00 plus transportation to and from the resort was another $140.00. Granted the time share is paid for but the cost of the other things was going to run us $2600.00 and we booked a 7 day cruise with Balcony for $1460.00.