Pros:
Nice natural setting in a forest with large open areas. Good variety. 2 sets of tees for each hole. Lots of different types of trees. Uncrowded when I was there (probably heavily used during the summer months). Centrally located on the island next to the airport, and easy access from the bike trail. Free to play (there is a donation box on one of the holes, so leave something). Well marked tees and good signs. Easy to navigate.
Cons:
Lack of elevation. The rough can be, well, rough. Watch out for poison ivy. 2 holes cross areas where there are walking/jogging trails, but there are signs telling people to beware of flying discs.
Other Thoughts:
A little hard to get to, especially from the mainland, but well worth the effort. Martha's Vineyard is a great place to spend a weekend. Rent a bicycle, explore the island, and don't forget your discs.