Pros
Shifts can be fun (depending on who you're working with!). Early shifts are great if you can get up at that time, I used to love being home before 1:30pm, especially during Summer!
Cons
I'll preface by saying the big boss was genuinely great, always helping on the shop floor and would always speak to you like a normal person, just a really nice guy! Middle management were another thing entirely. They didn't treat you as an employee - more like a naughty school child. Mega power trips. Understaffed and overworked a lot of the time, especially during summer. It was often impossible to put out half the food in the back, even if we didn't take a break. Weird rules around breaks too - you can't take it in the last hour before you leave, even if you haven't had a chance to take one yet, so lots of shifts we just...didn't take a break. If you told management, they'd just say it was your responsibility to fit it in. During Summer/Christmas periods when there was no time in the morning (because more food deliveries, and it all has to be on shelves by a certain time) you'd struggle to get one. And don't get ill, ever! If you do, expect to be guilt tripped to the eyeballs by your manager, or asked to find your own replacement for your shift. It's a hard slog, lots of lifting / dragging heavy cages etc. I would never go back, I still get chills when I do my weekly shop! If it's for a few months to fill a gap, go for it, but don't take it too seriously.