Pros
You can feel great about the place and the work you're doing. While many other financial firms are imploding and/or ripping off their clients, Vanguard continues to stand out as a steady, ethical company that does what's best for its clients. The people are friendly and the atmosphere is caring. The company tries hard to encourage people to build careers, and invests heavily in developing its employees.
Cons
Two drawbacks. First, while the brand is well known and generally respected among investors, it doesn't have the broad "sex appeal" of some other financial firms. You probably won't get an "oh, wow" when you tell people you work there. Second, the company tends to recruit primarily from local areas and tends to grow its own talent, so you'll generally find that peers' diversity of perspectives/experiences is somewhat limited.