We had good weather when we visited, so this probably helped our experience immensly but we enjoyed seeing the ruins of the fort and town. We also learned a lot as well. We are not from the area and had no idea a battle had been fought between the British and the Spanish on the Island.
It is hard to believe today but Fort Frederica and this Island was a major British military outpost. The result of the battle was that the St. Mary's River became the border between the British and Spanish and remains as the border between Georgia and Florida today.
Admission is still $3.00/person and we watched the 23 minute film in the visitors center before exploring the grounds. I highly recommend seeing the film before you walk around the grounds. It will really help you understand what you are seeing.
As others have said, there are only pieces of what once remained but you can definitely tell there was a village and fort located here and there are lots of signs to explain the excavations.
It actually is quite peaceful to walk around the oaks and Spanish moss and just take in the beautiful grounds.