To be any good I'd think they'd have to be somewhat closed at least in terms of compatible hardware drivers / benchmarks, and preventing piracy and malicious attacks. In that sense I don't think they can avoid going against everything that Linux stands for.
Of course, I don't expect regular gamers would give a shit but Linus Torvalds and his friends are probably going to tear this thing a new asshole for essentially being what Valve would claim to be avoiding on Windows 8 machines.
If it's all open, fair enough, but all the linux gaming talk at recent events appears to me as hollow unless they continue to support other distros with a client as good as steamOS, otherwise they've just forked and hijacked it really. It's another Android in that respect - somebody commercializing in the space for a specific purpose.
I'm willing to be impressed by it, especially in terms of cost etc.
