Apple today released OS X 10.9.3, after two months of developer testing



From MacRumors:

The last 10.9.3 developer beta, build 13D61, was released just over a week ago. The update, which is recommended for all Mavericks users, improves 4K display support on the late 2013 Mac Pro and 15-inch MacBook Pro with Retina display. According to the release notes, it also re-adds the ability to sync contacts and calendars between Macs and iOS devices using a USB connection and it improves the reliability of VPN connections using IPSec. The OS X Mavericks 10.9.3 Update is recommended for all Mavericks users.

  Apple Releases OS X 10.9.3 With Enhanced Support for 4K Displays, Syncing Improvements