Phone screens on top-end phones are high enough quality to manage (and are higher resolution than most PC monitors anyway). They also have the added benefit of being able to render graphics internally as opposed to being attached to a PC by a cord. Yeah, the graphics may not be quite as good, but the gap in perceived graphics quality between a $1000 PC and a flagship cell phone is rapidly closing.
I think the Rift will be the choice of the "PC Master Race", but a solution like this is much more mass-market friendly. There's no reason a headset like this should cost more than $30 once mass-produced - and that's low enough to be an impulse purchase for a lot of people.