How is T-Mobile's coverage in the Bay Area?

So I am thinking of switching over to T-Mobile in a month or two and wanted to find out how good their coverage is in the San Francisco Bay Area. Anybody willing to share their experience? I live in the South Bay region if that helps. And what about T-Mobile's coverage in most of the major cities? Such as NYC, LA, DC, etc? Or transportation ports like Minneapolis and Atlanta?

Thanks