Update: T-Mobile has also posted an update page for the LTE Nexus 7, which it identifies as Android 4.4.3, build KTU84L. We're still not seeing the update on any devices.
Here we go again. T-Mobile says Android 4.4.3 is coming to the Nexus 5 and Nexus 7 today. Bugfixes and security enhancements are all that's on the changelog, and the build version is listed as KTU84M. Fixes are always good, but we'll not be holding our breath over this one just yet — it's hardly a surprise, and we've seen carriers jump the gun on this one already.