A couple months late, but better that than never, right?! The reviews and opinions that I found on this site were such a huge help in making my decision to travel with Atlantis, and by extension with Royal Caribbean, so I want to make sure and spread the wealth a bit and offer some thoughts.
Basics: I traveled with my partner of 7 years - I'm 30, and he's 40. I've traveled relatively extensively (Ecuador, England, Mexico), and have taken two "straight" cruises with my family, both on Carnival, on much older "dumpier" ships :). The Liberty (Royal Caribbean) stopped at Labadee (which is Haiti - just a week after the earthquake; more about that below), Grand Cayman, and Cozumel. It departed out of Miami - we stayed there a few days beforehand in South Beach (one of our favorite places - we found a wonderful new hotel, the Cadet - gorgeous, cheap, and great location).
There were two distinct parts to the trip: Royal Caribbean, and Atlantis/the Gay Charter. RCL is first; Atlantis is below that.
Great location - near everything. Quiet cabin. Awesome shower.