Pros
Easy to meet some neat people who do not go to your high school and become good friends as you spend a lot of time working together. The work environment is super fun, even the early morning employee meetings because that's where you get to see all of your friends at once. Supervisors are pretty cool, and as long as you do what you are supposed to do and show that you are a responsible teen, they might let you come back during the summers between college. Where I worked, everyone starts out at the concession stand, but if you show you are patient and polite with customers and work hard, you'll be moved to something else. The best thing I learned while working at Cinemark in high school was how to answer and talk to people on the phone (this is done in the Box Office). It used to make me nervous, but I had a lot of practice so not anymore. Also: free movies, free popcorn as an employee. I definitely miss that.
Cons
Long hours of being on your feet, you will smell like popcorn. It can be boring on slow days, but that's to be expected sometimes.