Pros
I've worked at COS for two years now and overall I've really enjoyed my time there, the management at my store were very friendly and helpful, they do try to take in consideration if you've got uni or another job when rota-ing you for the week and the other members of staff were great to work with, the perks are good, decent discount which can be used at all the other H&M owned brands, you get to take part in staff sales, plus quarterly and yearly bonuses which is an added plus, and you also get decent amount of uniform twice a year (which you don't have to pay for!) I think the upper management do make an effort and do communicate with the stores on a regular basis, especially compared to other brands. Also if your committed to the brand then there are good opportunities to move up. Overall a great brand to work for (there's a reason why the staff turnovers so low!)
Cons
The only con is wage, considering the standard the staff have deliver everyday (especially when it's busy!) it could do with coming up a bit. For part timers it's fine but for full timers trying to make a living (not least those who live in london) it can be a struggle.