Vantaggi
Nice working location, most people are friendly, good benefits at HQ. If you have a great leader who is well liked and respected by peers and superiors, you may do well provided you are in the good graces of your leader. This will last as long as you and your leader remain the roles that made you successful and well-liked.
Svantaggi
Kelly HQ is very clique-oriented. You are in or you are out. If you are a favorite you will do well as long as you maintain your status. If you aren't - beware. Management subtly requires favorites to maintain their status with liberal bowing and scraping. If this isn't your cup of tea, look elsewhere. One line I overheard says it all: "It's not about what you know, it's about how well you're liked". Quality and quantity doesn't count as much as being "liked". Management also has a consistent habit of duck and cover. Don't expect your leader to put his or her neck on the line for you regardless of the circumstances. Those that make waves are removed. Sometimes, even those that speak the truth are removed.