We won a free trip there a few years back. The place is very nice. Bring your own big cups from home. That way you don't have to keep running back to the bar to fill up the tiny ones they always use at all-inclusives. Don't expect a lot of music native to the Jamaican culture. I listen to more reggae every day that they play in an entire week at that place. It primarily top 40 which I despise. Go to the sushi restaurant if they still have it and you like sushi. It's very good. The jerk shack is also good. Oh yeah... the diving.
We went there just after visiting Little Cayman, so we were a bit spoiled. However, we were pleasently surprised by the diving on the North Shore of Jamaica. We used our own equipment, so I can't vouch for theirs. The boats were modest, but did the job. We had one bad dive, where they missed the reef. We ended up exploring a 10' x 10' reef for about 10 minutes and then surfaced. There is a great wall dive that they can take you to. The wall is incredible. Lots of cool formations. It reminded us of Little Cayman except there was nowhere near the same marine life and the coral had some algae problems.
At one time, I'm sure Jamaica had some great diving. Unfortunately, it's been overfished and unprotected for too long. We even saw some fish traps underwater. Horrible! Don't let the down sides discourage you. We still saw some great stuff. You just have to look harder to see it. Visibility was great.
Scott