I have stayed at the Renaissance Ilikai(now gone),Ren Wailea(now gone) and the Kauai Marriott all as a Gold.
My absolute favorite was the Ren Wailea.Small,intimate,friendly and a great beach.
Kauai Marriott was ok-the beach was not attractive to us and the pool was so cold it was unusable.We spent most of our time on Kauai driving to different beaches,so our accommodations at the hotel did not matter too much,but the rooms were definitely in need of renovations.
We will be at Waikoloa this year on points-I am getting a bit nervous based on some FT comments,but since we are burning points after the recent MR changes,and it is Hawaii after all,I am hoping things will be fine.