Pros
Great place to learn and grow. Company (depending on the department) is still in growth stage making it better for you to cross train with middle management and other departments. Advance is very slow; they are very selective, but very possible if you work hard at getting noticed for your contributions to the team.
Cons
Most senior managers have egos. They have been with the company for quite some time...perhaps its why they are senior management not necessarily due to talent. Acquired skill and high turn around naturally lead most senior managers to inherit their positions. Now they feel prestigious for having a managerial role. If they would have to reapply for the same position they currently hold, it wouldn't be surprising if most those managers would not be hired to do their current job.