Don't take the 3 Stars as a negative; for the right person it's a definte 5 star.

The cruise on the Regal Princess was nice.   The most memorable part was the ships ability to win any fog horn war with other cruise ships.  The Regal blasts "The Love Boat" theme.  It brings a smile when it's done, and passengers from other ships cheer when they hear it. 

 We did not have any bad experiences, but it was not what we were looking for.  For new ship, the Regal was very nice, but there was no "wow" factor.  There was lots of elegance to the ship, but nothing awe inspiring.  I remember the 6-7 deck atrium on another lines ship and that stuck in my head; people 8 floors high dancing to music makes memories.  My wife and I are in our 40's and we felt extremely young onboard; the age of the majority of the people really set the pace for the activities.  We talked to many people, and felt the activities were lacking if you were looking for high paced entertainment.  I can't fault Princess Cruises for what they provided; it turned out we were looking for more than what they offered.  However, If you are looking for a relaxing cruise, a trip on the Regal would be an excellent choice.  The food was really good; though we did not try any of the specialty restaurants.  Pool area was nice relaxing setting; no slides or fun areas for kids though.  We did take advantage of the all inclusive drink package; it was a good value.    The shows were high quality, especially the onboard entertainers.  Probably best onboard one's we've seen.  Once again, theater is like the rest of boat; elegant, but not set up for flash.  We've seen some cirque de soleil type of shows on Norwegian; theater on Regal couldn't handle that type of set-up.  Did find it odd that they had no place to put your drinks in the theater other than holding cold glass in your hand the whole time or putting it on the floor.   The movies under the lights was excellent by the pool.  At night, the put cushions on the chairs and pillows out for everyone, plus warmed blankets.  Huge screen and go to see recently released movies.  TV in rooms was different.  Very few TV channels, but lots of movies/TV/programming on demand. 

Overall, if you are looking for an older crowd, with good food and great relaxation, the Regal is a top choice.  However, if you are looking for more excitement, or if you have kids, I'd look at other lines.