platform independant hahahahahahahahahahahahahhahaha
SteamOS is not platform independent - just the opposite! It's the Intel PC architecture.
If all you want to play is a Limb-o-like indie, then some little 200 quid fag-packet linux box (not including 512GB SSD) will be just gggreat. If you are wanting to play Dragon Age 5 or WoW with any decent framerate, you're going to be disappointed.
The reason the existing consoles work is that they provide a stable fixed target to aim at for devs. A continually evolving hardware bundle like the steam boxes will be will just not work.
Are you going to throw away last years SteamBox because this years version from Alienware has much better gfx? If you're a PC centric gamer, of course you are...that new game doesn't run well on the last years model you've got.
That's what you do all the time with your PC. New gfx card this year, oh a new PSU because the last one wasn't meaty enough, oh more memory, oh new CPU is out so new mobo and...
Valve don't really care - they are coining it in from you all right now ! You already have PC's and why would you no just connect up your pc to your TV? You probably already do. If they cared about games, they'd get around to writing some rather than milking you all just as much as Sony, Microsoft and Apple do.