If you're a member of the Windows Phone Preview for Developers program, build 8.10.14176 is now being pushed out to you by Microsoft.
The update includes performance improvements and bug fixes. The build should clear up the 80188308 error that some Windows Phone users were seeing while trying to install Windows Phone 8.1 on their phones.
Other problems fixed include the inability of the HTC 8X and HTC 8S to receive the Windows Phone 8.1 update. Those two models did not have the proper drivers installed, which caused Microsoft to stop trying to update the two handsets.
Lastly, more Lumia owners who are members of the Developer Preview program, will start receiving the Lumia Cyan update. Microsoft had started rolling it out for some models a few weeks ago. But the guys and gals in Redmond plan on speeding things up.
The Lumia Cyan update includes a new Start screen, the Swype-styled Word Flex feature, a file manager, IE11 password improvements, calendar enhancements, and an Action Center for notifications.