Pros
You are supporting your country, and some of the best people you will ever meet, American Soldiers. You get to see things and do things most people can't do, regardless of income. Occasionally, you get to witness history in the making, or make history.
Cons
Loyalty is not rewarded at all. Prehistoric categorization and compensation rules make it easier to hire someone "off the street" than someone in a temporary job who is already in the system. Some veterans receive extra preference, some receive none at all, for unclear reasons. Money available for training, equipment, etc, is feast or famine. There are quite a few slugs, many at the senior management level, who are doing just enough not to get fired, and react to change with hostility. There are now three different retirement systems in place, and they range from the incredibly generous to the embarassingly sparce. Under Rumsfeld, they implemented new policies designed to break the employee's union.