I am a university doctor from Sweden. I took a Ryanair flight three days ago from Copenhagen to Vienna without any problem. Today, I took the return flight. I was this time told I must pay a penalty fee for my exactly identical bag. I told them I came three days ago with Ryanair, with the same bag. Ryanair's staff did not believe me. I offered them the ticket as proof. They ignored it and shouted at me to 'pay the fine or you cannot board the plane'. I then removed a large duvet cover from my bag, after which the bag fit into their standard model box. Still, they ignored it, and repeated: pay or be left behind. Upon request, they also refused to give me their names, or the name of their manager. I also watched as Ryanair's staff showed the same disrespectful treatment to many other, visibly upset, passengers.
Know this before choosing Ryanair:
1) They can forcibly take a large amount of money from you at the gate without justification.
2) If you dont pay, they can threaten to not give you the service you have bought and paid for.
3) They are not necessarily interested in a civilized conversation, as was my case.
I have flown Ryanair regularly for over a decade. I must now reconsider my future choices.