Pros
Next is a good employer. Everything is organised; pay, discounts, uniform et al is really very well done. No delays or hitches. It also allows you to gain some leadership relatively quickly, as long as you're good. All employees are rated on a colour coding scheme, and if you're not good enough, you slip down and eventually you're gone if there's no improvement. Although they do help you quite a lot to improve. Stockroom: high paced environment. You need to be very quick and there is no time to dawdle or chat with other staff. You and your team are monitored in "units per hour" that are worked. You have an expected rate that you should work at or exceed. Fall behind and you need to explain why, and it has to be valid.
Cons
Sometimes, if your team has fallen behind for whatever reasons, you will be required to work unpaid to get it finished. Legal? I don't really know. Happens? Yes. Productivity is sometimes set to a ridiculously high company standard that can only be achieved if your stockroom and store is at the the best setup. Anything in the way, poorly organised or anything else will slow you down and put you at risk of slipping down the ranks.