Pros
Good pay after factoring in total comp (housing allowance, food allowance, free Healthcare and dental, Roth TSP with 5% match) Good amenities if you actually pay attention to newcomers briefs and go to the Army Community Center (ACS) and other support facilities on base to take advantage of the resources the Army has to offer (free gym and pool, subsidized daycare, free financial and legal services (financial advisors, AER loans, notary), Education Center (Army tuition assistance, certification assistance, on-base testing centers, etc) If you're an officer or NCO, the army puts you in many positions where you can hone leadership and management skills. I developed leadership proficiency as a platoon leader, learned cross-functional management and leadership as a company executive officer, and higher lever leadership and how to work with civilians as a dual-hatted MP detachment and Garrison HHD commander. Schooling benefits are great. An ROTC scholarship paid for my bachelor's degree, and the GI Bill plus the Yellow Ribbon program is fully funding my MBA at a private school.
Cons
Your mileage may vary greatly depending on a variety of factors. Your MOS/specific military job, being enlisted vs an officer, which branch of the military you're in, stateside vs overseas, garrison vs deployed environment, being in a training (TRADOC) unit vs a combat/combat support unit, the quality of your middle and senior management teams, how much effort you're willing to put in and grow, etc will all contribute to determining how many hours you work, how physically or mentally strenuous your job is, how efficient your organization runs, and how much work-life balance you have. A big one is probably the leaders. Many things like the interest-free loans the army offers, requesting a job change (e.g. reclassing from infantry to cyber), requesting to go to a specific army school, etc, all require your immediate or a higher level commander to approve. So the competency, EQ, and quality of your mid level and senior commanders/supervisors will determine how many and to what extent of Army programs/amenities you will be able to utilize to their maximum effect.