As you say I'm sure Valve saw the warning signs around Windows 8 and the possibility of Microsoft limiting 3rd party stores in some way. I believe SteamOS prob

As you say I'm sure Valve saw the warning signs around Windows 8 and the possibility of Microsoft limiting 3rd party stores in some way. I believe SteamOS probably gave them some bargaining power as a Dell AlienWare gaming machine was the only one Microsoft gave in to letting boot to something other than the Start Screen, it booted to Steam. This was during the period where PC/Laptop vendors were crying out to be allowed to boot to anything that helped users work out WTF was going on with their new PC :) Valve are getting developers on board slowly with Steam OS, the new Street Fighter being a pretty big release that has a SteamOS port at launch. They seem happy to play it slow at the moment, as always ;)