I've recently switched from Firefox to Vivaldi, for one reason: Firefox extensions must use javascript injection to capture keyboard shortcuts and mouse gestures. This basically kills all shortcuts+gestures that quickly change tabs, which is how I navigate 95% of the time.<p>I was a big fan of Opera, so I decided to try Vivaldi, which has built-in features for this.<p>After a few months I'm probably switching back again due to two problems:<p>- Vivaldi runs a lot of stuff on the main UI thread, leading to unresponsive interfaces (try the History Panel with a large history, it takes several seconds to type each character in the search bar, and just having the panel open slows down every other tab).<p>- The Android browser doesn't support extensions, and the ad-blocking is not as good as Firefox Mobile + uBlock Origin.<p>If not for those two problems, I would keep it. It's a great browser and I admire its passion for its own power users.