Hate them. They are so frustrating. I also tend to answer back when it's particularly pissing me off...
I've located the mute button which helps with some of it.
Just wish I could go to an actual check out, rather than be barked at by a person saying 'that one is free!' I can see but didn't want to barge past everyone else and their trolleys...or you.
Then proceed to have to wait 5 mins for the assistant to come and approve your alcohol, as heaven forbid tesco allow babysitting the self checkouts to be a job in itself, so the assistant is otherwise enthralled with sorting out security boxes. If you use the assistance button, naturally it freezes up the till rather than allow you to carry on while said assistant sorts out security tabs.
Oh, and there's security tabs on their bags for life, so you can't even get packing until they've come over. And there's rarely any plastic bags there.
Matalan are particularly annoying having quite literally turned round their employee tills, with a minor software update. There's no real space for your basket, so you have a pile of scanned/unscanned clothes. I take the hangers out of protest. I dont want them particularly but if they wanted them back they should have scanned my shopping. I only buy a few bits, I'd dread to have to scan £200 of kids clothes by myself.