just got back from the st. kitts marriott and it was great! as platinum, they upgraded us to an ocean view room in one of the out buildings (we were in cockleshell). If you go, i really suggest getting one of these rooms with an ocean view. we happened to be there during the full moon (harvest moon) and it was really neat to see it's reflection on the water. it was very, very bright. it lit up the whole beach very nicely.
the staff was great. it was kind of funny though, because it seemed like they were all showing up for their first day of work, lots of kindness, but often no clue.
we spent 6 nights there and did not get bored. there wasn't lots to do, but it was extremely relaxing. we went horseback riding one day which was fun and over to Nevis for a day. in the end, i highly reccommend visiting.