i really feel like trying this out as a quasi-firefox user, but i've really started to love and appreciate Zen for its UI :( wonder if there's a Waterfox X Zen alternative.

EDIT: whoops, should've scrolled down a bit on the website, looks like Waterfox has vertical tabs as well. damn, probably going to try to migrate to it sometime soon...

EDIT2: of course supports firefox extensions as well, perfect.

Firefox has vertical tabs as well, and it is a lot less bloated that the extension one I was using.