I'm a web app developer, and I started using Opera on Windows about 3 years ago. Since then, its become my default browser. It's common for me to have 12-20 browser windows going, and often 150 tabs open in all those windows at any given time.
I have an Angular8/Java REST web app nearing production. Since Opera is my primary browser, during development I got it all working with Opera, then I'd test using Chrome/Firefox/Edge. Next to Opera, Chrome is the best one that it works on. For mobile, I tested on iOS using Opera/Safari, and on Android I used Opera/Chrome.
My app has 100% functionality on Windows Opera, and it works about 90% on Android Opera, and 75% on iOS Opera. Since all browsers on iOS use Webkit, Opera, Safari, and others, perform about the same. Windows Chrome is about 90%, Windows Firefox is about 60%, and Edge is unusable. I do use Polyfills in my Angular development, but Firefox and Chrome still cannot achieve 100% functionality.
My app is highly HTML5/CSS3 dependent, which accounts for some of the missing functionality. It has a variety of controls, such as sliders, faders, toggles... Also, only Opera can handle the embedded controls that are in the many DataTables I have.
My audience is about 10,000 users that work in the IOTA Tangle - an encrypted data ledger. This audience should be fairly tech savvy, so suggesting that they use Opera does not seem unusual to me.
What do you think?