I haven't been, and I'm less than 200 miles from Memphis. Whether it's worth it, likely depends on what you're looking for - This is only the 2nd or 3rd yr for that show and in my opinion it's more 'commercial' than informative. For me, I'd drive the 700 miles to Frederick, MD for the Camaro Nats (and the original 1st gen Camaros) before I'd drive the 3 hrs to Memphis.
Are you going to drive your Pace Car the 900 miles each way?