Well if this is your first Atlantis cruise I can assure you that you will have a great time. Atlantis has a huge repeat clientele. I did my first Atlantis Trip in 2003 and have been on several since and I'm booked to go on the January 2008 Liberty of the Seas cruise. (which is sold out)
Check out the article I wrote a couple of years ago:
That will give you a bit of insight as to what you can expect.
You'll have a blast!