Pros
Great benefits and people to work around. For a production worker, I don't see a company out there who would do as much as they do for their employees as Millennium does. They have a lunch to celebrate successful months and often shut down the whole plant to hold team building games outside. The winner of the games gets to go in the money machine and catch as much money as they can. Seriously, tell me another company doing that? Heck, last year they even gave away a brand new car!
Cons
It can get hot during the summer, but they're constantly adding things to alleviate the heat and smoke. Curtains around the presses and fans to pull air across the plant floor.
Personality types are hit and miss here with incoming employees. Millennium will not allow an overly aggressive person to talk down to people for too long, this is a pro or con depending on who you are, but I recommend looking elsewhere if you have the reputation of being overly cocky about things.
Stay humble and thankful and Millennium will take care of you. Learn as much as you can and if they see you care, they will give you the time you need to learn.