I've done it the past 3 years. It is about as flat a century as you will find in the Asheville area. But it is not flat relative to those outside the mountains. I believe there is somewhere between 4-5K' of climbing on the route. It is well supported and well attended. The only gripe I have with the course is how many times it crosses railroad tracks. I guess that is just the way it is when riding in a river valley and trying to maintain as flat a course as possible.
I remember the Team in training riders on this ride. They all seem to be having a great time. Almost made me want to slow down and join them, but 5.5 hours is long enough for me on the bike.