SteamOS

I don't see how SteamOS can succeed, but they've probably thought this out better than me.

1. What is their target audience? The subset of PC gamers who are so dedicated and technically-inclined to install an entire OS just to game? They keep hyping "PC in the living room" - I'm just pointing out that it's not like ANY PC sold in the past year couldn't connect to a TV; even if it couldn't, this isn't something an OS can fix. Even if you have a desktop and can't run a HDMI cable, the solution is wireless HDMI or the Chromecast, not to buy a new PC.
2. SteamOS will not replace Windows. Saying you can save the cost of Windows on a gaming PC is like saying I'll buy a Ferrari, but I'm going to save money by not buying wheels.
3. So since people are still using Windows, what advantage, exactly, does SteamOS have? It needs to have HUGE performance improvements to be worth installing and maintaining a separate OS for.
4. People are not going to restart just to play games. I've tried. It doesn't work. If you don't believe me, try it for yourself - restart your computer before and after each time you run a game. See how long you can keep it up for. In theory, you could run Windows in a virtual machine. Apple uses this as a selling point all the time. In practice - it's much slower and has more hassles than people realise (e.g. copying and pasting between OSes is no trivial matter).
5. Saying you have a catalog of a million games is misleading and irrelevant. I spent $1000 on a gaming PC; I want to make use of my hardware, not play 1000 variants of Klondike solitaire.
6. Are they expecting enough support to get all hardware manufacturers to write drivers? I know, for big companies like Nvidia, Intel and AMD it's no problem, but how about other components? Networking? Keyboard? Mouse? USB headsets? SSDs?
7. We're living in a world where economies of scale are not only convenient - they're necessary. For this to succeed, this needs to not only catch on, but catch on in a big way. Do they think there are enough people out there technical enough to do this?

I sure hope they're putting more effort into Half-Life Episode 3 than this.