Pros
Active job with friendly colleagues. I can see how it would be a nice job once you've got the hang of it and like working independently. Loading up is a good workout and if you get out on time without any issues then it can be a genuinely pleasant job. Customers generally pretty friendly.
Cons
Little to no support from management, until you do something wrong. Genuine minor mistakes are met with the full force of corporate bureaucracy, instead of being headed off by proper training & support. Managers are either too busy or inexperienced (both?) to communicate properly and offer anything other than a "by numbers" approach. Even though John Lewis "partnership" talks the talk about being supportive and employee focused, the disciplinary procedure is bizarre - they make it seem like you're being listened to and treated fairly, but the outcome is pre determined. Whoever writes the HR procedures must be a big fan of Kafka!