Don't forget Firefox either; while Chrome has taken the lead in many areas, Firefox is still ahead in some (graphics acceleration and JavaScript language featur

Don't forget Firefox either; while Chrome has taken the lead in many areas, Firefox is still ahead in some (graphics acceleration and JavaScript language features for example), and more importantly, Firefox led the way in terms of innovation for years and years before Chrome was on the scene. Other open source products I can think of with fantastic UX are Transmission (the BitTorrent client) and Colloquy.