Pros
You must find opportunities to learn from others and you have the most impact to drive your own career. Nothing comes to you automatically. This is a place where people who take initiative can thrive. People around you are very smart and ambitious. Employees can learn a lot from the right mentor.
Cons
Your experience, performance, and opportunities are heavily determined by your direct manager's support, and indirectly, your skip-level manager. Regardless of whether you do good work or bad, the process is highly political. If you have a bad relationship with your manager, even if it isn't "your fault", you're set up for failure. It is, unfortunately, a pre-requisite that you manage this relationship first before your actual work performance, because little else matters if your manager does not go up to bat for you. For me, I was lucky to have supportive direct managers. For many of my peers, however, I've seen very poor managers and there is little the system can do to protect employees from bad managers. Crap shoot at times.