I tried Shake Shack for the first time a week or so ago.
Had a peanut butter milkshake and quite nice. Tried another flavour the next day and not quite as good but nice enough.
Then went back and had a burger and fries. Was sorely disappointed by everything. Sure the burger was medium (usually only touch well done) and moist, but no taste as such. The crinkly fries tasted of nothing.

Tried it again in New York at the weekend and exactly the same. Tasteless food although queued out the door for some reason.
Also tried one of their concretes and expected a milkshake sized cup rather than a tiny pot of bland white stuff (supposed to be chocolate etc. but was more like sugary wallpaper paste)

Had 5 Guys before Shake Shack and far far superior. Portions a lot better, tastier fries and burger etc.

In N' Out has nice burgers. Their fries are nice but prefer McDonalds especially if really hot and salty.