Went there once and never again.
Going in, I knew it would be overpriced for the yuppie neighbourhood, which it was (some $15 burgers) but the burgers were dry, dry, dry. "Sorry, we have to cook them at least medium well, city regulations."
Well Burger's Priest can cook them to order, medium rare etc. The reason is that BP grinds their own meat on the premises, hence they are not bound by the regs. For the price one pays at the Cellar, I expect to have my burger cooked to order as opposed to leatherised. How difficult can it be to to grind your own meat instead of having it shipped in, especially for a "gourmet" burger place?
A place (not necessarily for burgers) I like better a couple of blocks north on Yonge is "Stack", a BBQ smokehouse. A little overpriced, but they try for that southern BBQ style. Not totally authentic but reasonable for the neighbourhood.