Pros
Amazing customer service experience/training that you'll carry with you through your career. Pays 20p over the adult minimum wage, even if you're younger than that. 50% staff discount. They try to be a fun place to work. AMAZING company ethos (just doesn't always filter down). Fantastic opportunities for personal development IF your manager is one of the nice ones. (The smaller stores are the nicest to work for.) The lower level staff who work there are lovely people.
Cons
Highly target driven. Must be with a customer at all times or management are unhappy with your performance (even if there's only one customer in the shop and they want to be left alone). On your feet all day. You are never enthusiastic enough. Your jaw hurts from fake smiling so much. Highly variable environment between different stores - some amazing, others are managed by narcissistic micro-managers with nothing but criticism and condescension. Supervisors and trainee managers are not paid appropriately. Often asked to stay late. If you're working a store close, you will not leave at the time you're meant to according to the rota. You will often not be paid for staying late. In large stores, breaks are unreliable/poorly scheduled/you're often pressured to cut yours short, and they are never long enough. Hectic 12 hour shift during Christmas period = 1 hour break. You would rather go to work with severe food poisoning than deal with the repercussions of taking a day off sick. Highly disorganised - regularly given shifts on the day before the week they were for.