People say you can do it in an hour -- we wouldn't call that fun! The trail right around is easy to follow.
It is sealed along most of the east coast with the remainder being dirt or sand. At the southern tip, just to the west of the large deserted bar there is a staircase that leads to the highest point on the island. The views are terrific and it is well worth doing.
Be sure to take enough water with you as there are long stretches along the west coast where you can't buy any.