My Mom has been on a ton of cruises and each time she goes to St. Thomas she makes a pit stop at Star Jewlery. Her picture is even on the wall. She has gotten a number of pieces there and has never been dissapointed.
She gets it appraised back home and it always has appraised for at least double of what she paid.
They are also good with returning stuff. She bought a bracelet once for my brother to give to his girlfriend. When she brought it home it wasn't quite what he was looking for, so she called them and they took it back and gave her a full refund. Some places want to charge you a re-stocking fee.