14 DAY TRIAL // Valve is working on SteamOS version based on Debian 8, and it's making good progress with it. The operating system is still considered a Beta, and it's not ready for prime time, especially since developers are still making important upgrades.
SteamOS releases are not terribly exciting and most of the time it's just about a few updated packages. On the other hand, Valve is not trying to have anything exciting in their distro since this is not their goal. SteamOS needs to be as stable as possible and to offer a complete and carefree experience. This means that the only thing SteamOS has in common with the distros is the fact that it's based on one.
Developers know that SteamOS needs to be updated regularly, and they are doing a good job to keep everything as it should. The Linux kernel is a core component, so it's easy to understand why they would want a stable and proven one and now the latest stuff that you can find.
SteamOS gets a new kernel
The 3.18.x branch of the Linux kernel is the most recent LTS version available right now, and SteamOS devs have just upgraded to a newer version. It's not quite the latest one, but it's close enough (3.18.19).
According to the changelog, some xpad controller fixes have been added, a steamos-autorepair service has been added, some obsolete files have been removed, and a number of core packages have been upgraded.
As you can see, with the exception of the new repair service and the controller fixes, SteamOS Brewmaster update to version 2.30 is pretty boring. Also, please keep in mind that the systems still need a full HDD to install (unless you do other shenanigans), and it's still under development. Testing this on a production machine is not recommended.
You can download the SteamOS Brewmaster version from Softpedia and give it a try.