Longtime lurker; seldom a poster. I'm hardly an insider for Vol info, but since there's a discussion about hamburgers -- on THAT, I'm an expert.
Shake Shack is popular with New Yorkers who don't know a good burger. Not that it's awful - just overpriced, undercooked and blah.
Whataburger is good. In-and-Out is great. Culver's is my favorite. Pal's is fine; if I lived outside the Tri-Cities, I'd think it was great. Fatburger is good. Steak n Shake is a small, cheap version of Culver's. Freddy's is comparable to Culver's, and we have some of those around the Tri now.