so the whole company is crappy because of one dead zone in your office? i'm sure you can find dead zones on any network.
when you compare things like customer service, rate plans, at&t's refusal to support tethering (which t-mobile allows), and phone availability (how many android phones does at&t have?), t-mobile doesn't look that bad.
This is in Seattle btw, I was on T-mo for 4 months, and coverage will drop to zero in the most inexplicable urban spaces.