When I was stationed in Germany I had a buddy from Chicago that would always rave about Portillo's in Chicago. Needless to say this place warrants such praise.
I've had everything from the Italian beef, the burgers, the hot dogs, the cheese fries and shakes. Everything is great, the staff is efficient and work their tails off.
Walking into this place is like walking back in time, it reminds me of a ballpark blended in with a soda fountain (minus the fountain). There's tons of seating and even though the line will probably be long, it moves quickly. You're also able to watch as your food is prepared, a point they definitely emphasize as a differentiator.
Portillo's, at least this Tempe location, is a top notch fast food restaurant. If the Chicago locations are better then I'll definitely have to try them, because this Tempe location has always been solid for me.