Of course it has been a success. I (half-German, half-Croatian) grew up in times where each of the borders from Germany to Croatia had anything from 1-4 hours of waiting time, you'd need to exchange currency at each border (at outrageous rates) as well simply to be able to pay for fuel and food, and heaven forbid you even got a call on your phone due to roaming charges.
Nowadays? No border controls at least on the way to Croatia any more (the other way around does because of certain far-right politicians), no currency exchanges, no leftover currency when you go back, seamless cross-border bank transfers, no phone roaming surprise bills... it's utterly awesome.
For what it’s worth, I’m in favour of the euro (and further EU integration).
The friction between Ireland and the UK is near zero, both have different currencies.
This isn't to say there aren't benefits to the Euro; on an individual level of course not thinking about exchanging or exchange rates makes life easy. It's simply not palatable to the UK, Brits or the core financial institutions by which its service oriented economy excels.
Indeed, Schengen and Euro were only introduced this year - but I lived through how all of the old crap slowly got dismantled, each year it was one annoyance less.
The most painful thing is to see how many people want to dismantle all of that progress.
I was a remainer and I'd love to rejoin and Schengen, the mobile roaming stuff, etc. are all wonderful and I would like them back.
I'm not convinced the Euro would be a good idea and I'm absolutely convinced that you'd lose public support for rejoining if you tried to go that route.
I keep wondering if EEA + Schengen would be a viable middle ground.
Nowadays when I travel, I just pay with my usual bank or credit card and get good rates without thinking about it. If my bank didn't have good rates, there's Revolut.
The main pain is that the EU hasn't standardised payment systems. So in parts of NL and Germany, you might find your Visa isn't accepted because they only take Maestro, or, in Sweden, Swish, for example.
[1] https://www.conradbastable.com/essays/the-germany-shock-the-...