Just thought I would post this because I have been getting so many questions. If you have any more questions feel free to send me a pm.
Yes, Chang is a beer. That is why I said it was an area of expertise, not an area, as in a location. Other things not to miss: Sticky rice with mango and coconut milk at Mom's and Pop's (Tonsai Beach), stuffed banana pancakes at the Chill Out Bar (Tonsai - must be made by the special gourmet chef), banana shakes, magic shakes (although I would not recommed drinking many of them at once), swimming during full moon (the bioluminescence is strongest then), renting a boat to check out the numerous other deserted islands, doing one of the tower climbs out of a boat, snorkling at one of the farther off reef islands, etc, I could go on like this for a long time. Don't miss Phra Nang beach, it is rated as one of the top 10 beaches in the world. Definately be prepared for many beautiful topless women (and men I guess). If you agree that the thong was one of the greatest inventions of the 21st century (second and third maybe only to the assembly line and the Model T car) then you would be pleasantly suprised.
Definately do Humanality (5,6 pitches, starts with a 5.8 tree climb Tarzan that is really actually in the 5.8 range, tied off branches for pro, stepping onto the 3,000 lb stalagtite on the second to last pitch is amazing) and one of the multi-pitch routes on the Taiwan Wall (Lord of the Thais is supposedly the bestone)
Climbing in Krabi pretty much refers to the climbing in Railay. You go to Krabi, then taxi or bus to Ao Nang, then boat to Railay. You can take the bus (very cheap - extremely long) or fly roundtrip from Bangkok to Krabi for around $100. Don't get ripped on the taxi, around 400 baht. 50 baht for the final boat ride to either Railay or Tonsai.
Tonsai and Railay are within a short walk and are both close to numerous great cliffs. Tonsai is cheaper in terms of food, accomodations, etc. so there are usually more climbers there. The beach is not as nice though. Railay is nice and more expensive with a nicer beach. (The two places beaches are separated by a 5-10 min. walk. There are more people in the 30-50 yr old range at Tonsai and more younger 20-35 at Tonsai. Of course this is definately a generalization.
You can also stay on Railay East. In my opinion the farthest from most stuff and the worst of the 3 beaches.
I would recommend the King climbers climbing guide for one major reason - it gives climbs stars. This way you really know if climbs/cliffs are worth doing and you hit the really awesome ones. The book also has better desciptions. The newer books have shitty bindings and generally fall apart (Note a new binding may have now come out). It is older so is missing a few great walls. You can get beta for these though.
In all, best of luck and hope this is helpful