if i tell you my history, you might understand better why SteamOS is true answer for some ppl like me. being avid linux fan from 94 and avid gamer i had 2 choices. use Windows all together (completely unacceptable) or dual boot to play and work. that time i decided to go with 3rd optionm console just to retain my pure linux work environment. and truthfully, i was really happy with my decision as PS just worked which was never true for gaming on windows and i never looked back... until PS3 came it all looked fine and dandy, but lack of support, constant extremely bad network lag, removing features... well, not a happy camper anymore. then comes Steam which runs on my favourite OS, i can run it any way i want... HELL, YEA!!!!!
i never, ever installed even solitaire or tetris on my work machines. while i have around 150 games for ps3 and 100 for ps2. and yes, i lose those in any case no matter which next-gen i decide to go with. but, jumping on steam wagon with pure steamos+steambox now enables me using OS of my choice (which was my original wish), retaining console feeling (i really started to like console and having work separated) and never lose my library again (pain that came with every next-gen is gone), not to mention my console somehow became free to use in different ways. my main gaming machine will be defacto stembox+steamos, but this time i might consider buying some notebook which can run games too since my library will be shared between console and my working OS.
as i noted in second answer there are 4 basic ways to implement whole "I play games on Steam+Linux". SteamOS+Steambox is just lowest denominator of those aimed at specific public like me. as far as old pc's... no, they never said that. proclaiming that would be a blatant lie. all you need is search any valve steamos article and you'll see what they really said. well, in short
- they won't restrict you where you install steam in any view (hw, software, distro), but that doesn't mean it will play everything with full settings
- they plan to set development gaming hardware margin for gaming companies to target. this one was always the terrible side of pc compared to console. if you develop for console you know exact hardware you need to target for everyone using it. for pc... not really. they always told about 3 spec categories (good=streaming only, better=can play games and serves as low machine standard for developers to rely on which is steambox, best=build it your self from rocket science parts). they also said they plan to incorporate hw checkups whether your system can play some gome or not.
- their box and their distro is nothing but set standard for what and how to base on when you want to make it work for your machine or your distro or for developer to have a stable test bed
to clarify you one more thing, otherwise you might be downright terrified right now if you look their "better" hw specs.
i7 and 970gtx? i mean how is that just better, but remember long cycle of console and speed pc hw goes obsolete. in 2 years any 30EUR graphic card will be just as fast. and in 2 years you'll having hard time even finding computer as slow as that no matter how low cost it is. it is a long play game where PC really benefits and linux even more
but, that doesn't make it as no 970gtx, no playing for you. it just means that you won't be able to play 1080p/60fps with stereoscopic 3d enabled.