When the 50 pence coins first appeared, there were people who complained that it was all wrong, and coins must be round, dammit, and that the sharp edges would cause tears* in people’s pockets, and what the hell was ever wrong with a proper ten shilling-note anyway? (History does not relate, but I imagine this was a delightful chance for these people to have conversations that did not entirely consist of complaining about the weather not being as good as when they were young. )
Now I think of it, I suppose there would have been difficulty with vending machines at first, but pretty soon they all caught on, given that vending machine proprietors are in the business of wanting to take money. I have had annoyances with vending machines that want a pound but can’t cope with a pound note, however.
*That’s “tears” as in rips in the fabric: it’s the lack of coins that cause the tears as in weeping, of course.