We’ve done a lot of reporting about the Bell OS 126.96.36.199 for the BlackBerry Storm. It started with a few leaks as well as the ability to download it unofficially from Bell before they announced the news. You can now download the OS officially from Bell so don’t worry about exploding your device with a bad download.
Although this is official, it is only from Bell. Don’t expect AT&T to help you with customer service. As always, backup your device and take all necessary precautions before proceeding.