Talking over Valve's announcement of its Steam Machine prototype specs with a few people online (including Ars' own Andrew Cunningham), I've come to the conclusion that Valve might need more than its own free, standardized gaming OS (and, ideally, an exclusive killer app) to make PC gaming appealing for the living room console consumer. To really put up a fight, they should do something to simplify the dizzying variety of architectures and performance points that are inherent in parcel with PC gaming.
Just look at the range of hardware configurations that Valve is including in the roll out of its Steam Machine prototypes. They range from machines with parts totaling $600 or so to Nvidia Titan-powered beasts that would cost upwards of $1500 to build. Valve is also quick to mention that plenty of other companies will be rolling their own systems to market, some of which may deviate "substantially" from the prototype. Yet all of these different configurations are falling under a single "Steam Machines" label.