I've always felt it was less about the shop and more about the artist. I would always recommend researching the artist thoroughly. I've seen good and bad come out of almost every shop, and sometimes it's just that the artist didn't quite fit with the piece's vision.

Then some people just hop on the Friday 13th tat train and ride it for fun. Guess it's about what you're after and the time, work and cost to get it. Some people have VERY long wait times.