Pros
Get to see the steel industry up close and in the plant. Interact with the plant workers and the management staff. Fast paced and fairly exciting. Depending on your mentor, can be assigned good projects for your internship. I learned a ton about hardware and general plant mechanics (oil/hydraulic systems, safety, union dealings, etc...).
Cons
Fair amount of busy-work, but that's to be expected as an intern. A couple of the projects were pretty boring (ex: excel datasheet manipulation, inventory cataloging, etc...). I really didn't use my knowledge of ME at all during this internship. If I were to take a job after the internship, I would be hired as a shift manager for the maintenance department, which is not at all what I wanted to be doing (even though the pay would be decent).