This is such a great option if you're looking for last minute camping, but note that it can be pretty competitive! I'd show up early to see if anyone is leaving and set up before going hiking.
I've stayed at a few of these and they're all great. The ones on Avery Creek are more traditional style and some of the other ones are park and "hike in" like 100 ft or so.
Please read the information linked and practice LNT if you choose to camp here. The park service doesn't have capacity to clean up these sites so please leave it better than you found it.