Vantaggi
Learn a lot in a very little time. If you want to know about data communications business, this is the place. If you can survive the grind in the first year, you tend to do well anywhere in the long run. Other than P&G this is the place to learn about marketing and sales. The only place in fact in high tech. I learn't more at work than at business school.
Svantaggi
In a large company and particularly in large business units it is inevitable to have mediocre politicians, who sullify an otherwise excellent atmosphere. Your competency may not always count. Sometimes the mid level leaders can be absolute idiots as well, so you have to watch your back even if you are competent and doing everything right. In other words do your stuff well, but learn basics of being a politician and always watch out for mediocre idiots, they could potentially damage your career at CSCO.