The Nexus 5 and the Wi-Fi only version of the Nexus 7 (2013) slate are on the receiving ends of the update. The former is receiving the KTU84M build while the Nexus 7 (2013) is receiving KTU84L. You need to be using stock Android to grab Android 4.4.3. Since the update is sent out on a staggered basis, be patient. If it doesn't come today or tomorrow, don't panic. It will eventually arrive.
And for those with other Nexus models or Google Play edition devices, you should soon be receiving the Android 4.4.3 update. The hot new feature is the dialer for handsets, although the update does exterminate a bug that was messing with the battery and the camera on the Nexus 5.
source: XDA via AndroidCentral