Pros
Grow up fast. College totally paid for, and then some. Some paid travel to fantastic locations. Many of the people are fantastic, lifelong friendships, etc. Get a good perspective on what "suck" actually means which, seriously, kind of helps you throughout the rest of your life.
Cons
The headline of this review. Sometimes your travel opportunities can also be severely stifled, with you being assigned to some podunk for years on end with virtually zero travel. Performance evaluation system leads to things being fixed that ain't broke, constantly, usually to your detriment, sometimes to your extreme detriment. Information is withheld from you and then you get chewed out for making uninformed decisions. Directives often are initially delivered along with a threat. Everyone gets treated like the dumbest, most foolish person out of 300,000. Culture of making things harder than they have to be, making things suck that don't have to, sucking the fun out of activities that should be the coolest things in the whole world that you could be doing for a living. You might wind up getting supervised by someone who is dumber than anyone you meet for several years after you depart the service (but I do have to reiterate that a lot of people are great, as I mentioned in the Pros). Imagine if the DMV completely owned you. Your job is not to do your purported job, which itself is probably pretty cool. Your actual job is to work to overcome the (often arbitrary) hurdles that the bureaucracy puts in your place to obstruct you from getting your job done. *That's* your actual job. If you think joining the military might suck but you've had sucky jobs before, consider that the fact that your previous sucky jobs were probably in the neighborhood of 40 hours a week (give or take), and you could go home to your regular home, and quit the job if you had to, makes a much, much more profound difference when you're *really* stuck with a job.