Pros
Job security, can't get fired, guaranteed promotions, relatively easy to become an officer (OCS and some ROTC programs), medical benefits, leadership experience, "time off", pay isn't as bad as people would believe.
Cons
Time off- 2.5 days off a year. This is pretty awesome, but there are limitations. Most units will not allow you to take a 4 day weekend without being charged 4 days of vacation. This means that most companies that would charge one five days time off for M-F, the Army charges you 9. This is a big difference that often goes unnoticed or checked. Deployments are horrible. Some jobs are significantly worse than others. Promotions are based on time in grade and time in service. If you are an over achiever, then the military is not for you. You have to stay in at least 8 years to be recognized and promoted early. This will only get you promoted a year ahead of the worst of your peers. Even worse, most of the officer evaluations reports are subjective and completely dependent on your boss. Speaking of boss, as I mentioned earlier, you get promoted based on time and service and time in grade; therefore, you have a good chance that your boss is no better than you are at your current job. Chances are, your boss will be grossly incompetent and riding out their 20 as well.