Pros
Sometimes you get phases where you've just got some really good people working beside you. There was a really good social environment and despite leaving the company around 5 years ago I still have some very good friends from my Tesco days. Staff discount!!! reduced stuff! You can hide promotional goods and keep them for yourself (such as grommit mugs)... not that I would condone such behavious of course
Cons
Management isn't always great. I've had some great managers whilst working there some of which are still up there in my top 5 managers.... but then you do get some numpties that just haven't got a clue what they're doing, or what you do, or what the team does day in day out. Full time positions are scarce Overtime offered tended to be last minute... Even when it was predictable (covering long term sicknesses and the bereaved etc). This made it difficult to plan your free time. They got rid of the pool table.