Re: Hololens isn't VR...it's AR..
WRT to Steam, SteamOS is coming along pretty well, just still in beta/testing. It's never been claimed as anything else that I recall. Sort of hoping that the GDC conference has a bit more info. It's 'launch' has really been series of announcements of progress on SteamOS and info about how hardware partners would work with them and what to expect from them.
As for Xi3 (makers of the piston), they worked with Valve for a bit in the early days, then backed out - Valve mentioned that they had worked together but have since gone seperate ways - probably after a senior person at Xi3 started banging on about how awsume Windows was. Xi3 then continued to use Steam terminology to fluff up their PR, saying that the Piston was the first commercially available Steam Box, even though (more likely because...) partner hardware is called Steam Machines....
Basically Xi3 are a pretty shady bunch when it comes to their association with Valve, and I'm prepared to cut Valve some slack on that one as I got confused by it too back in the day.
Source? Google and widely known facts. Plenty of info on the Xi3 debacle here.