Mahogany Run is a challenging course, but you can find those anywhere. What you can't find anywhere is golf courses near the ocean, with ocean views. Unfortunately, you don't find that on St. Thomas either.
We played golf at the St. Lucia Resort & Country Club. We probably deserved what happened to us, because Carnival cancelled the excursion citing "difficulty with tour operator," and we chose to book it anyway directly. We got there to find a large tournament occupying the whole course. We got to play the back 9, and that was all.
One of us played golf, the other took the "Rail and Sail" excursion. The golf gets a '5' rating: approachable course with wide fairways, spectacular views, and friendly and helpful staff.
Scenic Railway Rating:
Unfortunately, the "rail" part of the Rail and Sail excursion was cancelled due to a mechanical breakdown, so we sailed up and down the coast on the catamaran. It was a nice enough time, but not what we had paid for.