That's right, Android 4.4.4 KitKat is in the midst of pushing out, the major changes revolve around a security flaw related to that nasty HeartBleed debacle in OpenSSL that we are still cleaning up from. You have changed all of your passwords lately, right?!?
Since there is actually very little new for me to say here, I'll just fire you over to my Android Authority post for the particulars. Or, if you are 'in the know' the factory images for Nexus devices are available on the Google Developers website.
Have you seen the update yet, any hidden goodies that we haven't seen yet?