Firstly this is a JW marriott hotel, so not much can go wrong here. From Phuket airport, Kaho Lak is roughly 1 hour away.The hotel is huge, well maintained, has an amazing pool and great views. We stayed in the 1st floor room that overlooks the pool. The ground floor pool access rooms looked awesome (wish we had taken those). The pool runs throughout the hotel and is huge, with 2 pool bars. Food is awesome, though expensive.
The 4 days we were there, 3 days it was continuously drizzling. However that didnt stop us from exploring the hotel or Khao Lak for that matter. Drinking by the pool bar, in water with water falling on you is somewhat cool I would say (Even though I was shivering :)) The staff lady at the bar was kind enough to make me cocktails without ice!
We hired scooters for rent, which are available just outside the hotel and rode through Khao Lak. We also booked a local tour package offered by the hotel (Sightseeing, boat trip to James Bond Island etc). The tour was worth it.
There is a very cute and cheap restaurant just on the side of the resort with some extremely friendly guys. Do try it if you want a change from the hotel food.