I used to use Opera a lot many years ago. Back when it was faster and generally better than Firefox and IE was still a disaster.
But I think today there are better choices. Firefox has come a long way and will work seamlessly with 99.99% of all sites out there. However after trying out the New Edge browser that came with Win10 I have to say I was very impressed.
In back to back speed tests Edge loaded every page I went to faster and more completely, even those loaded down with cr@p like Microsoft, CNN etc.
One problem I continually had with Opera was it's inability to work seamlessly with many Financial/Bank Sites. This may well have been corrected. This even though I had it set to mimic IE.
I liked Opera for it's clean GUI and other features but I still think it's a definite third place browser now.