As promised Microsoft have begun rolling out the WP 8.1 Update 1 for developer preview users. The update, similar to the WP 8.1 update consists of two different updates two separate updates: 8.10.12400.899 and 8.10.14147.180, after which you’ll have the Update 1 on your phone.
To grab the update head to Settings> Phone Update> and check for updates. (provided you’re enrolled in the developer preview program of course).
Features in this update include Cortana for China, UK and Canada, as well as start screen folders, Voice over LTE and much more.