Pros
A good store manager leads to an excellent store experience. Hours as far as retail went were fair and the supervisors/managers can sometimes work it so that most if not everyone get rotating weekends and holidays off. If you just have to deal with store management (and not higher up) and they are good then you'll probably have a relatively positive experience. As a Shift Supervisor you'll learn a lot about leading people and multitasking. If you going for a Business Degree and you are in the right situation you'll learn a lot with this job and it will be enjoyable.
Cons
The pay for the job of the Shift Supervisor is not worth it. We are expected to do what Managers and Assistant Managers do. If you want the experience that is fine and actually a positive. If you are more financially inclined it gets really annoying (especially when you see some of the Assistant Managers they hire and that get fired about two weeks later). From District Manager on up there seemed to be a massive level of disconnect as far as communication and expectations for individual stores went. I was constantly "loaned out" to other stores to make room for payroll. This was something I enjoyed a lot at first because I liked gaining the experience. The problem is I would be told one thing and the Store Manager of the store taking me on would be told another. There were managers being told I was their new full time employee when in fact I was told I'd be there for a week or two at most. In addition these stores were at least 45 minutes away from where I lived. I was told I'd get compensation for gas mileage. Did I? Nope. Then of course one time I got a manager who didn't understand that if my car has broken down and I live 45 minutes away from the store that I probably can't help out that day. The Unions: It's a double edged sword. It's not the Unions themselves, it is the position it puts you in. Sometimes they help you a lot. Sometimes they don't care about you. If you are at a Union store and a Shift Supervisor then (at least in NY) you are in the union (or just have union dues taken out and not be). So you are a union member and also effectively a manager. It gets sticky sometimes weeding through interests and the Union rep usually doesn't make it any easier on you.