Pros
Excellent benefits package, including 4 weeks of vacation when you start (plus a week off between Christmas & New Years), and the most generous retirement plan I've seen anywhere (complicated formula, and the specifics are in the process of changing, but essentially they match at 2-3x the employee's contribution). Workplace environment will vary wildly depending on which department you're in; mine gives me an extremely high degree of freedom, autonomy, and flexibility.
Cons
You can't spell "bureaucracy" without "BU". Offices such as HR, purchasing, payroll, IT, etc can be infuriatingly opaque and inflexible to deal with for even very simple transactions. Salaries are not as generous as in the private sector. Opportunities for advancement may be limited, as there is a tendency to fill even low-level management positions from outside hires instead of promoting internally.