Pros
Career opportunities are definitely one of the best reasons to work at Vanguard. Management is very concerned with having the right people in the right job and they therefore are interested in getting you to a position that you'll be happy and satisfied with. New opportunities open very frequently as employees rotate to new departments and areas.
Cons
Compensation is often a complaint heard from many employees and the truth is that when you are the "lost cost provider" of mutual funds, you've got to keep a tight lid on spending. It's important to realize that while the salaries are smaller relative to the rest of the industry, the overall benefits should weigh just as heavily for most people (healthcare, profit sharing plan, education reimbursement, bonuses, company prestige, advancement opportunity, etc.)