I don't think that SteamOS/Steam Boxes are designed to be a general-purpose operating system. Although it is a derivative of Linux, it is focused primarily on gaming, and therefore it may be more apt to say that it competes with consoles and not general purpose operating systems.
As far as my general purpose OS, I tend to have both a Windows installation (will definitely upgrade to Windows 9 when it hits RTM) and Linux installation (currently Linux Mint). Some of the changes in Windows 9 sound like they are making the right decisions - for example, bringing a version of the start menu back and enhancing the Modern UI API so that apps can be run in windowed mode.
As far as consoles are concerned, I don't actually have any consoles at the moment, and I'm not too likely to get one anytime soon. If I would have to choose one in the next few years it would most likely be a PS4 or XBox One, though, instead of SteamOS... but I would prefer to wait until the next generation because - since they are both on x86 architecture now - it should be much easier to get backwards compatibility (so I won't miss out on any games, in theory). SteamOS will likely lack major releases for quite a while, but I am hopeful that publishers will port titles to it. If Valve is smart, they might even release an exclusive like Half-Life 3 or something to SteamOS (which would definitely make me install it)!