Re: As a Presto lover
If you mean the original Opera and not specifically the rendering engine, then my answer is yes. I used Firefox for quite some time but Vivaldi returned just in time when Firefox messed up sidebars, tabs and plugins.
That said, from a web standards perspective I would prefer if Vivaldi used Gecko instead of Blink as rendering engine, but I suppose it was easier to base the overall browser on Chromium rather than Firefox.