I've been to the five guys in allen. It was very very good. I'll admit, while I was there, I ever so slightly wished it was a In-and-Out burger (and next time in Allen I'll go there), but not *nearly* that much.
The FIL had never been to Five Guys (in spite of living in Allen). He's a fairly big fella, so he asks for their 'largest' burger. My admonition to stick to the standard burger (he is also a pretty macho fella) fell on deaf ears. I think he was satisfied
My wife decided to figure out how to get a smaller meal next time. You americuns are nuts on portion sizes!