With bugs like the missing month of December in the Contacts app and Bluetooth stuttering, many say Android 4.2 had the most bugs an update has had since Honeycomb.
Luckily, the 4.2.1 update is coming and it seems to be adding the missing month of December, as well as fixing the Bluetooth issues. The update is merely 1.1MB, so don’t expect any huge changes except for those bug fixes, but at least Google has managed to deliver the update before the actual month of December arrives.
You should get the update over the air in the next couple of days if you have the Nexus 4 phone or Nexus 7 / 10 tablets.
source: XDA Developers, Talk Android