I stayed there a few years ago. St. Kitts is a very friendly island. The locals are very proud of the fact they've managed to maintain their quiet island appeal, however it is changing as more and more developments pop up. We did not rent a car and had great experiences with all of our taxi drivers. We were running late for our ferry to Nevis, and I was looking in my purse for the fare - the driver insisted that I pay him when I returned because he didn't want me to miss the ferry. He was there waiting for us at the end of the day.
I think you'll enjoy the resort. There is a small grocery store within walking distance and that's about it. The amenities are great. Some people don't care for the larger resorts but I enjoy the convenience, and the St. Kittian hospitality abounds, even at a large property like the Marriott.
I used points and I still got upgraded to a very nice suites with views of caribbean.