We booked a private all day tour with Lawrence of Antigua, based on recommendations from CC folks. It was awesome! We saw the entire island, including the Devil's Bridge, Betty's Hope, Nelson's Dockyard, and got to finish by spending 2 hours at Valley Church Beach.
The island itself is a "5+" -- gorgeous, very mountainous, with one vista surpassing the next! The tour we booked through Carnival was a "3" -- Town and Country Drive, around 3.5 hours. We did get to see much of the island, including Pusser's Landing, but the tour guide himself was a little lacklustre.