Pros
GBS was pretty hard to handle with all the traveling, utilization, etc, but working as a consultant for different companies gave me a great deal of experience and exposure to pretty much all the experiences you want to have during your lifetime - from sad to funny, from beautiful to ugly. Exceeded pretty fast by working hard, and giving it my all. But that was when the economy was better.
Cons
Depending on which group you're working in, there are not too much personal relationship that you develop in GBS. The manager that supposed to rate you, doesn't work with you on a daily basis, and in most cases have never met you before. Reviews strickly rely on the people you work with that will report to this stranger who'll give you a rating your bonus, salary, and future depend on.