Five Guys prices for fast-food that's just above McDonald's quality. I have only eaten at a Carl's Jr. a handful of times in my life and it's probably been about a decade since I last gave this franchise a try. I don't recall thinking it was anything special then, and my opinion probably isn't going to change anytime soon.
Carl's Junior serves a pretty big "$6 burger" on a brioche bun. The bun is phenomenal. The burger that's between the slices is mediocre. Splurging on the combo gets customers a bigger drink and more fries than any one human being should ever try to consume. I recommend saving at least a buck and half and skipping the fries, the burgers are big enough to satisfy your appetite.
Being attached to the US Airways center gives this location a little bit of a unique feeling. It's a convenient lunch or dinner spot for downtown workers (and the handful of downtown residents). It's also an option as a place to get a bite that's going to be a bit cheaper than whatever you would order at an event inside the arena.