I've been using Linux regularly for the past half decade and daily for the past year as a PC (as opposed to as a development and deployment target for 12 years). No, it's not viable. Not when the competition is Windows and OS X. I'd explain why, but it'd devolve into a huge rant about poor UX, drivers, audio services, file system snafus, grub upgrades gone wrong, bad advice on forums compounding problems, all of which get brought up ad nauseum in any Linux thread. Linux is very good as a server, but that in no way translates into being a good PC.
And no, Chromebooks are not a desktop, they're "browser appliances".