Pros
Fun people to work with, lots of drinking if that is what you want. EMS providers provide great experience that is invaluable when moving to real companies.
Cons
Basically expect to be treated like a commodity. They will use you and work you long hours without OT for salaried positions. When business is down, they have massive layoffs. You will never feel secure working for this company. Pay is below average, benefits are below average with only 2% match in 401K and no pension plan. Expectation to travel can be quite high in some positions with little regard for personal inconvenience in one's life. Promotions are based on fitting the Jabil mold. I knew some managers who were the best I have seen told they did not fit the Jabil "personality" and as a result would not get promoted.