Steam has once again surpassed its previous concurrent user record, which was 11.1 million as of October 31, 2015. Currently the peak today is 12,331,307, with Dota 2 peaking today at 904,373 players, followed by Counter-Strike: Global Offensive at 652,925, and Fallout 4 much lower at 116,599.
It appears the Steam cache issue, which exposed user’s data, is not slowing down the PC gaming service at all. As noted on NeoGAF, last year on January 2, 2015 the steam concurrent record was 8.5 million. You can view the Steam statistics as of this writing, as well as a simple graph I put together using the “Peak Today” data to show the scale of the top two games compared to the rest of the top 10.