Pros
There is the patriotic answer that you are doing service for your country, and that is true, but the job is a real adventure. I change duty positions every 2 years. I am trained as a pilot and project manager. I am routinely thrust into unknown environments and sensitive positions where I am forced to figure thing out quickly or bad thing might happen. Talk about a rush, I travel internationally, get paid well, and I'm held in high esteem by my family and community. Yes, the conditions are sometimes tough and there is the issue of family separation, but the job is never boring, the training never more critical and the sense of accomplishment never more real. Its not for the faint of heart, but then again, I'm seldom stuck in a cube farm wishing to be somewhere else.
Cons
Life threatening situations, 24/7 duty hours, unexpected interruptions to personal schedule. physically demanding work, restrictions on your freedom of speech, lengthy family separations and subject to the whims of our political leaders. Many don't feel the benefits outweigh the demands. You have to be in it for more than a paycheck or you'll never survive.