We went to St. John in Nov. 2008. We flew in and out of St. Thomas, shopped a little, ate lunch and took a taxi back and forth to the St. John's ferry. I didn't notice St. Thomas being dirty, but it's very expensive (food, transportation, etc.) St. John was also very expensive - we shared a house with friends and rented a car. We have friends that own a restaurant on the island, otherwise I don't think we could have afforded to eat all week! Groceries are about 3 times what they are at home and the restaurant prices make WDW look cheap.
You can get some great deals on houses in the off season. Ours was beautiful, though pools are very small on the island. I did miss having someone clean the room for me
The Jeep cost us about $400 for the week. You need 4 wheel drive as there are huge hills - sometimes I flet like we were going to tip over backwards. They drive on the wrong side of the road!
The locals are very poor in St. John - I'm guessing the same goes for St. Thomas. They didn't seem very friendly to tourists (I'm used to Mexico and WDW friendly people), maybe because their cost of living has gone up so much with all the mega rich people buying houses on the islands.
St. Thomas and St. John are beautiful, but the resort we stay at in Mexico is even more beautiful and a week all inclusive cost us about 1/2 of what our St. John trip did. Our friends keep wanting to go back to St. John, but I think after our trip to Mexico this May they will be hooked.
Don't get me wrong, we loved St. John and it was great to see our friends who live there, but the expenses once you get there make other vacation destinations much more attractive.
Feel free to pm me if you have any more questions.