I ultimately think creating a dedicated distro as "SteamOS" (eg, will likely be a skinned Ubuntu) will bite them in the rumps.
I liked the idea they originally had - just a client that was pretty much guaranteed to work on Ubuntu (and later, assumedly - other major distros).
IMHO, the whole factional nature of Linux puts a lot of people off, esp. non tech people. I've always been a pretty big advocate for Linux, especially to people who have older hardware that want to wring some extended life out of it. Time and time again, I hear "if it's all the same base OS, why is there 200 different flavors of it?" from people that don't understand the distro concept.
Just a few weeks ago a friend got a hand me down computer from his work. Still a usable machine, but running Windows XP, which is coming to end of life here in another few months. I recommended Linux for it, as all he really wanted to do with it is browse the web and the like. He wasn't familiar with linux and spent the entire weekend installing various distros before calling me Monday morning shouting "I wasted my whole weekend trying 10 different variants of Linux and I can't tell the darned difference between any of them! Which one should I stick with???"
For us familiar with Linux, we all have our personal preferences - mine is Slack these days, but the sheer variety of distros can be extremely puzzling to people looking in from the fringes.