Did use plugshare and although their are a fair number of options, very few are level 3.
Made it there and back...but it was not easy. Stopped in Anderson at the Bleckley Inn (super nice folks) and although it was level 3, it was an extra 20 miles of driving and a 90 minute stop I would not have made in a gas car or with a supercharger in Greenville.
Charging in Asheville is all level 2 and required a 10 minute walk each way to charge and then retrieve car. Not the end of the world but not at all convenient.
Stopped on the way back at the Orchard Inn in Saluda. This is only 25 miles from Asheville but is level 3. Spent an hour topping up and crawled into Atlanta with 16 rated miles left.
Had I gone my normal speed I would have had to stop in Commerce for an hour or two.
I don't take many road trips but after this experience I would hesitate to recommend a Model S to someone who does.
Frankly, as an enthusiastic owner I am surprised that I reached this conclusion. However, facts is facts.
As an aside, the day before I left, I put my destination in Asheville into the Nav. It routed me to the Supercharger in Macon!
And then on the way back from Asheville, it routed me to the supercharger in Charlotte! Might be wandering around still had I followed those routes.