Similar to the October results and other recent months, the reported Linux use continues to float right around 1.0%. While last month there was the one year birthday of the Steam Linux client and more games continue to be made available for Linux, there hasn't been any dramatic rise in the Steam Linux use. I wouldn't anticipate any major change either until the Steam Machines are out and the Linux-based SteamOS or when we see any tier-one Linux launch title from any Steam publishers.
Via the Steam Hardware & Software Survey, Ubuntu obviously dominates the list. When adding in all the reported distributions the total is right around 1%. Even if giving all of the "Other" operating systems to Linux, it still would be coming in shy of 2%. The updated survey results can be found at SteamPowered.com.