When SteamOS released at the end of last year, there were some features missing. Not just Steam features either, as drivers and support for AMD and Intel chipsets were also missing. There were work arounds for it, however Nvidia cards were clearly the best way to use the new OS. This situation hasn’t lasted long though, as SteamOS has been updated to now support these neglected cards.
The update has exited beta, and now available in the stable branch of SteamOS. The update also includes update for the controller firmware, updated formware from Debian jessie and fixed audio. You can read about the various other minor updates from the Steam post, however the important to note is that if you’ve already installed SteamOS, it will automatically update.