Ease of use
Ecosystem (apps, drivers, etc.)
SteamOS is really just a login shell for Debian/Ubuntu when it comes down to it. For those unfamiliar with shells, they are simply environments you log into. You can choose which shell to use when you login. Unity and Gnome are such environments. SteamOS running on its own shell means that it will be more efficient and there will not be any background programs. I downloaded the shell off Steam's own site (just a normal .deb file so double-click install) and voila SteamOS on my existing Ubuntu installation. All I needed to do is login into my account. While downloading the whole SteamOS Beta may be very annoying, installing Ubuntu and installing the shell is quite easy and there would not be a need to wipe your hard drive. Personally, I dual-boot Ubuntu 13.10 and Windows 8. Ubuntu's installer is fairly intuitive and simple to use. And of course, you can install other Ubuntu/Debian based operating systems like Mint if you prefer. Despite the fact that the Beta requires Nvidia graphics, the shell runs fine with my Intel HD 3000 graphics as Ubuntu does not require any drivers for integrated Intel graphics. So really those limitations Valve imposed on the Beta aren't really limits inflicted on the shell but rather the OS. You just need to have drivers installed for whatever graphics card you are using and the build they have available for download only has Nvidia drivers preinstalled. SteamOS really isn't much different than big-picture mode right now, except for the cool Beta sticker, but it is worth installing as a shell. Performance is better since it launches in its own shell after all. I have also installed the whole Steam OS Beta on a desktop with Nvidia graphics, albeit I have since ditched it after finding out there was a stand-alone downloadable shell. I would not recommend anyone download the whole Steam OS Beta... but I highly recommend trying out the shell itself! Installing the shell requires installing two .deb files (on Ubuntu) off Valve's site specific to your architecture (32 Bit/ 64 Bit). For those unacquainted, .deb files are to Ubuntu what .exe files are to Windows.
Updated detailed review