[geppetto]

I've just gave it a try but nightly is still on the older version here. Anyway Firefox Preview is my default browser with Firefox Beta as a backup on Android. Preview is much faster but lacks extensions and many settings. Moreover I'm not sold on the new UI: address bar at the bottom is fine as long as it goes on top for some tasks, history is hard to find and I miss the favorites sites start-page (have to create groups but it's not the same).

I use Firefox over Chrome because Google - you know... there's a submission a day about that - and I trust Mozilla much more to be-not-evil and such. So it's kind of a political-ethical thing. On PC performance is on par so it's not a compromising choice. On Android Chrome still has an edge.