I have ATT and it works great, there are 2 places near the JeffCo airport where it drops but that is it.

Quality coverage is also dependent on the phone you're using. I use a 5yo RAZR phone which has a terrific antennae, it works in the elevator at my job from basement to 4th floor. I used a different phone for a couple of months and it dropped calls in both places the RAZR drops and in a whole bunch of other places.