Developer Preview 12/10

[mgfootballer]

If you've got Update 3 for Windows Phone 8 you’ll see two software updates from Microsoft. They are:

Microsoft Update 8.0.10521.155
Microsoft Update 8.0.10517.150

Installing right now. On Migrating your data (Step 3 of 6). Will update when completed

EDIT: Update completed, I would suggest restarting the phone after it is complete. Haven't noticed anything big (Others haven't either), but some of the lag has improved? (Might be going crazy)

 

[Laura Knotek]

That is correct. WPCentral had a blog post about it. Windows Phone update rolling out to phones with Update 3 | Windows Phone Central