I do believe it does depend on the store manager you get.
in my personal experience my manager did not really communicate, give feedback or support. I spent the first 4 weeks 5 days over 7 front of house serving customers and that is it. I did not feel that I was an assistant manager at all but a shop floor assistant!
A lot of the time when I display things, the next day I would come in and it would have been moved. I would price something, the next time I would come in and it would have been changed. Sometimes by only 1 or 2 pounds, and once by 50p!
They are under staffed, you are always covering other store, sometimes at the last minute.
You are expected to know everything even when you have not been told or shown or even when you have been shown once 4 or 5 weeks ago but are expected to remember!
When i started there was no hot water in my store and a broken toilet seat. this was the case way before i joined, the toilet seat only just got fixed when i left nearly 4 months later and still no hot water. The manager was always chasing it up with no luck, this shows how little they regard staff/volunteers.
You rarely work with your manager.
No praise or positive comments even if to say that you are improving so for me personally it was draining and deflating as it was non stop stress.
You get weekly visits and daily calls from higher management just saying have you done this are you doing that constantly. It could be such a great job were you can work had and have fun but not with management that does not boost morale!
they want you to put 50+ items out a day and keep a log of how many items you have been putting out, plus write an a4 page full of everything you did, what you sold for the next person coming in. You serve, keep the shop tidy, sort donations, steam clothes, gift aid, price, put out, take in donations, print tickets, etc and half the time you are on your own. which is fine that is the job but even after all that you are told it's not enough you have to do more.