Pros
Discipline is built into the Army structure, so whether you already have it or feel that you need it, the Army is equipped to serve those needs. Where else can you built yourself up from nothing, with a safety net there to protect you from your young, ignorant self. It teaches you priorities, time management, leadership, punctuality, integrity, personal courage, commitment. . .I could drone on and on.
Cons
Okay, it's not for everyone. Not everyone is well suited to having every aspect of life practically dictated to you. Not everyone is well suited to "technically be on duty 24/seven." Not everyone can handle being forced to respect those who outrank you, but just plain aren't nice people. But that's with any job. There are some sacrifices to be made in the Army, but overall, the good things that it has to offer far outweigh the not so warm and fuzzy things.