St. Thomas' main town is a haven for trinket shops and Diamond International jewelry shops, but don't let that deter you from enjoying the island's friendly people and amazing scenery. It is the "typical" Caribbean island with amazing blue water, gorgeous beaches and tropical landscape. Just be sure to leave the immediate port area and head out to Magen's Bay or some less congested part of the island.
St. Barts is a piece of Europe dropped into the Caribbean Sea. The first thing you will notice upon arrival to this French island are the herds of luxury yachts stacked up in the harbor. The port area of Gustavia is a charming, walkable town (just be careful of the traffic, in which there are no rules whatsoever). Enjoy one of the water front cafes or visit one of the high-end designer shops. This is a very wealthy island and it is easy to forget all about real life here and pretend to be a celebrity for a day.
St. Kitts doesn't offer much in terms of activity (the main port area of Basseterre should be avoided), but the natural beauty of the island makes up for it. If you go to one of the island's high peaks, you can see the Atlantic Ocean on one side and the Caribbean Sea on the other. Another interesting spot is an old fort which has much history to enjoy, complete with cobblestone walkways and cannons.
The Dutch side of this island, St. Maarten, has become an overcrowded cruise ship mega-mall. We were in with 4 other ships during our visit and the immediate port area was stressful, to say the least. The best bet here is to drive to the island's French side, St. Martin, and enjoy the peaceful beaches and upscale eateries and resorts.
Grand Turk, in the Turks & Caicos chain, is the most idyllic island paradise. Grand Turk was practically our ship's own private island. There is no need to take an excursion here or get in a taxi - the beaches, restaurants and shops are literally at the pier. Just step off the ship and you will be in paradise. This was a surprising port and I would gladly pick an itinerary again that offers this stop.