That Marriott is WONDERFUL! If you go during the Chinese New Year the entire island becomes one big watergun fight! It is SO much fun it is like being a kid again! I have never had so much fun in my life. The resort is beautiful and the people there are wonderful! Also you can get a massage on the beach there. It is a gorgeous hotel. It is in a remote area of the island...it REALLY is incredible!
HI we go there every two years there is a local shopping centre which is a little expensive and the main town of Patong is around one hour away. As is said its a lovely peaceful resort . Have you thought about Marriott Khao Lak quite close by but my favourite in the area especially the pool access rooms.
I've stayed at both the JW and Renaissance Phuket- both have shuttles from the airport, and both are great properties. I would go the JW over the Renaissance, things are a bit more refined, however both are great. If you're from the US; they're both unlike any JW or Renaissance resort you would likely have experienced in the US.
Could I suggest though, check out JW Marriott Khao Lak, resort and spa? Again, there's a shuttle from the airport (Phuket)- it is a bit further away than the Phuket properties, but certainly worth it- part of it was washed away in a tsunami a few years back and they have rebuilt everything since. Managed to sit back and have a drink with the GM on my last visit there, and was fortunate enough to learn a little more about the history of the area, and how it is different to Phuket.
Phuket is fun, its great, however for something a LITTLE less-touristy, check out the JW in Kao Lak.