Camped here with a large group spread over two campsites. We pitched tents right by the water which was awesome. It was quiet, but there wasn't much separation between campsites and often found other campers just people-watching the entire trip.
With Gatlinburg nearby, and the overall size of the campgrounds, it felt very touristy and not like a typical camping trip. While we had fun, we probably would not return for these two reasons.
Elkmont is a 40 minute drive from Clingman's Dome, which was, as one of my friends put it "the greatest experience i've had camping, ever". Great trails to be found all over the place, too.
No cell service available, which was also great, if you care about that.
We were a large group (16 people) and reserved grounds at Zilpo for a 4 day trip. We wanted to ensure we were close, so we chose H loop sites 35, 37, and 38. 35 and 38 are right next to each other, so it was easy to walk between the two, and 37 was rather secluded and used primarily as overfill sleeping grounds.
Overall, the campsite was great. We went during the end of August and it was really quiet. The lake was a muddy and murky, but that's typical for a man-made lake. The showers had no warm water, but we'll take a cold shower over no shower.
Electric hookups worked perfectly. Two people brought electric vehicles and were able to plug into the TT-30 outlet and reported no issues the entire trip.
There was cell coverage for all the major cell phone providers, which was a negative in our opinion. But that's totally your preference and I don't take that into my star rating.