BurgerFI - Avon, CT
Been twice. Overall thumbs up. Similar menu to the Shake Shack (my favorite fast food burger of all time), with a couple of additions (BTW Shake Shack remains undefeated in first place still). Burgers, dogs, a couple of "healthy" burger options, fries, rings, frozen custard, beer, and wine.
Decent burger, ok char, potato roll so holds up well and they toast the bun which I like. Up to two free toppings (sauces, etc.) cheese, bacon etc all extra as you would expect. Have some interesting things like blue cheese, fried egg, etc., not normally available for fast food. Burgers are all natural grass-fed beef according to website. Hot dogs are split and grilled, also on potato roll. Nothing spectacular, decent beef dog. Fries were excellent the first time, just ok the second time. Think Five guys skin on style. Onion rings are the size of your head, giant rings, just ok, probably won't get again.
I would choose the burger over Five Guys - better char on the burger, not "squished" with wrapping and the bag Five Guys insists on even if you are eating there. Fries are about equal. The frozen custard is a nice option, especially given it's right next door to a fro-yo place :)
If you like a decent burger, it's a really good fast food option (albeit MUCH pricier than most fast food).