Time will tell. San Pedro (and Belize overall) grabs some people more than others. We have done a good number of island and beach vacations to different spots, and enjoyed them all immensely. One of the questions we always ask after the fact is "would we go back", which encompasses a lot of factors. The people, the food, the location, travel aspects, lodging, diving, snorkeling, and just everything rolled into the question. Most places had at least one annoying factor to consider, no matter how minor, just a burr under our saddle. San Pedro (especially the people) got us to the point that we don't even consider being annoyed at anything. The laid back atmosphere just grabs some people and everything else just becomes less important.
So, go there, experience the place. Talk to the people. Eat stuff you don't normally eat. Relax. At the end, pose the question to yourself. Roll everything into a ball and measure it against your relaxation factor.
You may be the next AC-a-holic.
There are a few people that weren't impressed with the place, but only a few of them frequent this board sporadically.