Ball, was just out there last week. Nice place.
I have to say, though, Puerto Rico and what they call the "Spanish Virgin Island" were MUCH nice than St. Thomas...
If you have a chance, you can take a puddle jumper from St. Thomas to either Culebra or Visques for about $40 dollars r/t. Both are less than 20 miles from ST and much nicer as far as beaches go.
If you do go to Culebra, check out Flamenco Beach, it gets named the nicest beach in the Caribbean almost every year. There is also an amazing bioluminescest bay on Visques that will blow your mind. (you glow in the dark when you swim in the water from the small plant life!)