We've always enjoyed our visits here (eight in the last dozen years) and have booked six solid weeks of sand, sun, and pool this year.
Unfortunately, tourism does have it's ugly side. Most of Patong Beach, the main tourist beach on the island, is not fit for swimming. Karon, Kata, and Kata Noi to the south of Patong are usually better options with Nai Harn, even further south being the best choice.
Long tail boats for hire. It's a great way to cruise around, even to some of the closer outer islands, but be ready to pay.
The Tsunami did extensive damage to many of the beaches on the western side of the island but just about all was back to normal a year later.
Being a beach destination, there is little in the way of local Thai culture. Just about everything for tourist here is at least double what you would pay in Bangkok or Chiang Mai.