Pros
In some ways, Cisco still operates like a nimble start-up constantly reinventing itself. They are quick to adapt new technologies and innovations as long as that is where the market is heading. Change is the only thing that's constant, and they have no qualms to sacrifice long beholden programs or projects - in other words, no sacred cows. All this said, these are what I believe keeps Cisco successful, plus you gotta love their new slogan, "To be the best company in the world, and the best company for the world".
Cons
It is a big company, and you will feel invariably feel the beauracracies largely attributed to big companies. To get promoted you really have to invest considerable amount of time doing all the extra other things. Time that you would normally like to spend with your family. However, if you are satisfied with your current level then the workload is comparable to silicon valley standards.