Every time I visit the Chicago area, I make it a point to stop by Portillo's Hot Dogs. The food is fabulous. The staff is always friendly and helpful and the place is always clean. The food prep areas are visible, so you know there's no funny business.
They once gave me the wrong food. They quickly took it back, asked me what I wanted and had a manager refund me the difference with a very pleasant and responsive attitude. They apologized for the error, but didn't dwell on it. They fixed it and made it right.