Windows Phone 8.1.1 (build 14219) and firmware 02540.00019.14484.37028 are now live starting at 1 pm ET. Users can head into Settings > Phone Update and 'check for update' to grab the necessary files. If you are enrolled in the Preview for Developers program, you can leave it enabled.
Lumia Denim brings numerous OS fixes and changes to Windows Phones, including Hey Cortana for passive voice listening and Lumia Camera 5.0 support with HDR, Dynamic Flash and faster shot-to-shot times.
Source: Microsoft; Thanks, Aakash S., for the tip!