I've camped at Shady Grove multiple times and each experience has been great. I live nearby and it's a great oasis to quickly escape the rat race in metro Atlanta.
Originally built by the US Army Corps of Engineers, it's now operated by Forsyth County Parks and Rec. They're doing a terrific job of maintaining and upgrading the campground.
Very good to excellent mobile phone reception. Supermarkets are 10-15 minutes away.