For those not on the developer preview, you can now get the new Nokia "Black" update for the Lumia 520. Started rolling out on Thursday.
The big thing is that it adds Bluetooth 4.0 LE support.
Awesome, gonna update my 520 tomorrow. Thanks for the heads up Jessica.
Here is also a quick list of all the updates in Black:
Lumia Black includes some under the hood optimizations, Bluetooth 4.0 LE, camera improvements and greater support for Nokia software. Update 3 from Microsoft brings Driver Mode, custom ringtones for text messages, and the ability to close apps in the task switcher, to name a few.
Hopefully, tap to wake now will work for me, cause it didn't with the Amber update.