Starbucks coffee is utter garbage. If you want quality coffee, I can give you five other coffee shops on State Street which serve coffee that doesn't taste like it was filtered through an old muffler.
Why four stars, then? The service. I have never ever been made to feel like I'm bothering them when I order my drink. THAT is why I go to Starbucks versus the hipper coffee establishments down the street. This location has the best service I've ever seen ANYWHERE. I've never seen such friendly baristas. Is the coffee spiked?
Look, if you work at a Starbucks near campus, you're going to deal with all sorts of characters: bratty undergrads, random homeless, impatient businessmen who have important meetings, etc, etc. I've never seen an employee lose their cool. In fact, they look like they're having fun most of the time.
Come for the awesome service, stay for the meh coffee.