I was just there this spring and loved every minute of it. The folks at Cruz Bay were very freindly and helpful, they even let me slip in a freebie dive the day before I left. I don't recall there ever being more than 6 divers on any given trip.
One sight that stuck out was Angel Fish if it still exists. They were telling us that the Army Corps of Engineers was going to move the reef (not quite sure how you go about doing that). It's considered a beginner sight (this was my freebie, while others were doing there resort dives) but it was loaded with beautiful critters (no angelfish beleive it or not). I saw about 5 puffers (look closely under the rocks and outcroppings), stingrays, etc. I wish I could remember the other sights I hit, but of course I've lost my logbook which is my usual reminder.
I haven't been to all that many places (Tortola and Martinique(only 2 dives each on a cruise), Aruba, DR, Grand Cayman and St. John). St. John ranked 2nd only to Grand Cayman in my book. You will love it!!!! Oh yeah, don't skip the night dive. There were tons of glowing critters to the point that I was chasing my own fins just so I could see the explosion of light that they created. Tons of lobster (big ones) to and from what one of the local bartenders told me, you are allowed to take them out of the water near the hotel. Just check on the area, a lot of the island is considered a wildife preserve.
I'm a little jealous now, thanks for letting me relive that trip and reminding how much I loved that trip...enjoy!!!
Jeff