Never had any issues traveling by Ryanair. The Cabin Crew PA's can get a little tiresome on longer flights.
FWIW, I spent a great deal of time recently attempting to find a bag that was the maximum IATA dimensions and had to come to the conclusion that these more or less don't exist. (I am sure they do but by FAR not readily available in the UK at least).
The best I could get was around 55x40x20 (or maybe 55x45x20 etc). Instead I bought one which was too big (61x46x27) or something like that and have traveled with it as hand luggage on Ryanair anyway.