A new update is out for Counter-Strike: Global Offensive that could change the game in a big way. Now when you're using headphones (which should be always), the utilizes head-related transfer function (HRTF) algorithms to enhance sound positioning. What this means -- in theory anyway -- is you can track sounds better (like the footsteps from that guy creeping up behind you). You can hear it for yourself in the video below (use headphones for best effect).
If you don't like the effect, you can disable it, of course.
Other changes include public joinable lobbies, and optimizations and gameplay changes to the Nuke map.