Pros
I've learned so much in my 5 years so far, including (but not limited to): 1. I've learned (and become almost native-level fluent in) Mandarin Chinese. 2. I've learned a lot about leadership. 3. I've learned to be more self-disciplined. 4. I've gotten into great shape and health, and I've learned how to maintain it. 5. I've made life-long friends.
Cons
1. So many rules and regulations make me feel too micromanaged (like a child). 2. The way things look "on paper" are often more important than things that should really matter (like the welfare of your soldiers). 3. The promotion system is broken. I've been E4 for 3 years and still counting because of an even larger issue: recruitment. The Army recruited so many in my MOS (job) that all the slots in higher ranks were filled very quickly.