We dived 10 times in October and we only repeated twice. There are plenty of different sites but you will have to decide if it's worth your while. We were new divers and really enjoyed it. the dive masters will do there best to have you dive different sites if you go multiple times, they are very good.
Have not been to CTI, but went to CSS, which share some of the dive sites, in Aug '08. Diving in Jamaiaca is not like Cozumel or Belize, but it is diving in warm water. The corals are smaller than what we were used to, but there were a couple of decent sites. If you can get them to take you there, the Briish minesweeper Katherine was by far the best dive we had. Good corals on the wreck and a couple of good swim thrus alongside.