Great for buying cheap drugs that require prescriptions in the U.S., private beach clubs, Mayan ruins, and silver. But Cozumel has seen better days; it is a bit run down compared to prior years. You will not get "turista" though if you eat on the island; standards have improved lately.
Boring. Most of the cool places were destroyed in Hurricane Ivan. High prices. Good for stretching your legs. Only tours worth it are ones which let you see things in nature. The island is very safe and has a high standard of living.
The tours are very good, great place to buy art, booze, and ceramics. Watch it, much of the island does not feel safe. Very friendly people though, most of who are charming. Get a recommendation for a good restaurant on the ship.