The first beta of 10.9.2 included FaceTime Audio and was build number 13C32. Subsequent betas brought the ability to block certain iMessage or FaceTime users.
Today's 10.9.2 beta is build number 13C59. Its focus areas include Mail, Messages, Graphics Drivers, VoiceOver, VPN and SMB2.
You can get the update from the Mac Developer Center or via Software Update if you are currently on 10.9.2.
Read More [via Vicky, Bill]