We took a cab to Mountain Top once, and it was kind of dissapointing. There is a great view of Magen's Bay, but other than the view, there is not much else to do up there. There are a few shops with the same type of stuff you can get in the little mall near the cruise ship pier.
Yes, you can get a Banana Daquiri from the place where they were "discovered". They cost $6.50 two years ago, and to be honest, they make better ones on the ship. The view from Mountain Top is essentially the same as the view from the St. Peter's Greathouse, and they give you free rum punch there.
I've still never done the tram, but would like to. Lately, we've either gone to St. John, or to Sapphire Beach during the St. Thomas stop.