I've been to Five Guys a few times now. I think their burgers are much better than what you get at most fast food places (like McDonalds and Wendy's just across the street), but it's still behind really great burger chains like In-N-Out and especially Cook-Out (whom I've separately reviewed).
Their fries are pretty good and are along the lines of the old Boardwalk Fries places. A big peeve I have, though, is that when you order a basic burger-and-fries combo, they put your burger in a bag and then dump hot fries right on top of it. If you don't rip your bag open to get at your burger (or eat all your fries first--and they do tend to give you a lot of fries), you end up nearly burning your fingers trying to get at your burger.
I found the staff to be really friendly, efficient, and quick. I don't mind the pretty limited menu that's in line with a "do few things, but do them right" philosophy, but they could probably improve on the unfinished floor. That and the cheap tables and chairs they have seem to unnecessarily drag down the rest of the place.