I have (semi-daily) and would say it’s somewhat close to being day to day usable. They recently added Safari-style back and forth gestures and you can choose to arrange your tabs vertically (though not in a tree).
The main thing preventing daily driving is that it’s not in the App Store yet, leading to it not being selectable as a default browser. I also experience occasional crashes with hundreds of tabs open.
It’s essentially a better Safari, but (and this is what makes it the ONLY alternative to Firefox) with tree style tabs.
Progress has been rapid and the interaction with the dev(s) has been great. I see a bright future ahead for this browser.