Pros
Good benefits, job security, good pay for average employee. TSP (401k) matching is excellent, as is pension. There are small bonuses available, but one has to be on a noticable and successful project to get them. Alternative work schedules are good, but they need to go farther.
Cons
Unfortunately, the pension, generous base salaries, and the virtual inability to be fired means that the average employee lacks an incentive to be innovative or leave for other opportunities. This leads to a conservative & insulative culture that tends to be more inward looking rather than risk taking. The hiring process makes it difficult to get the best employees with specific skill sets. Some federal benefits are quirky and not easy to use compared to other large private sector employers. At the executive level, pay is often not commensurate with the private sector or even other agencies. Work from home policies are a must.