Pros
Extremely unique. You have a chance to really hone your leadership skills and each day is never the same as the last. You'll meet a wide-range of people from all over the world. The sense of camaraderie between many folks in the Army is very strong.
Cons
The US Military is a very socialistic system. Promotions are time-based, not performance-based. The quality of junior soldiers and officers can vary widely from excellent to terrible. Once these individuals are in the military it is very hard to remove them from the military if they are sub-standard performers. Some soldiers use the military as a welfare system and do the absolutely bare minimum to get by and because they never do anything particularly wrong, there isn't much you can do about it.