Pros
This review is about the non-HQ experience: If you're an extrovert and like working hard with other smart and hard working people, GA is a great place. For the most part I enjoy the fast paced environment - it keeps things exciting and there's always a new challenge to try to solve. Because GA campuses tend to be tech community hubs (lots of events and guest speakers), it's also a great place to grow your personal network.
Cons
Don't expect much on-boarding, training or mentorship at GA (at least outside of HQ). You're expected to figure things out on your own quite quickly and there aren't many opportunities for professional growth. After 1-2 yrs, most employees move on to greener pastures where they earn more and are involved at a more strategic level.