I have paddled and hiked the Big South Fork pretty extensively. Its really a pretty nice area. I would say its not quite as nice as a lot of the Tn/NC border areas, but close. I have done a lot of it because its close to me and, in spring, has a nice whitewater run. They now have pretty nice park facilities too.
The JMT is a good walk mostly. Its mostly wet with the exception of the area at the angel falls overlook and to the north for a few miles. So if you camp there, it will be a dry camp. Just south of the overlook, though, you drop down to lots of water.
My favorite parts of the park include angel falls overlook, angels falls at river level on the east side of the river(great for swimming), and falls branch trail from Bandy Creek campground all the way to Angel Falls.
Edit: Forgot to mention the arches throughout the park. There are several nice ones but double arch is my favorite. It would be a short side trip for you though.