Just now I got a notification that a 235 MB update is waiting to be downloaded. Do you have any ideas what update is this? I'm using Lumia 525 Windows 8.1 preview for developers. (Firmware version - Black.)
I'm also getting some update now, I was on the latest 8.1 DP.
Actually not the latest, I missed the 400 one, so this could be it.
Or Cyan/GDR1 Hope it's the later.