Pros
You get to learn a lot about a global company and there is something for everyone at the headquarters. The company is very relationship driven (which can be a downside) and there is a lot of emphasis on "chatting over coffee." The headquarters is a great place to be and there are a lot of perqs (all you can drink coffee, etc.). If you have the opportunity to work at headquarters I would suggest being a part of the product testing group (anyone can join). It's great to be able to have a sneak peak of future drinks and food and to be a part of how they are perfected.
Cons
It's a coffee company and they don't appreciate (at least in the department I worked in) people actually LEARNING about and being excited about the product. Just like any company, politics rule the show. Sometimes you can cover them up with whip cream, but there are still politics resting underneath. It is VERY relationship driven and just because you perform your job well, get fantastic reviews, and complete all of your work does NOT mean that you are a "good worker" in the Starbuckian world. Work-life balance is encouraged for people with families (read "kids"), but those without children are expected to take up the slack. They try to be innovative, but many of the long tenure partners strike down innovation from the "newbies."