UPDATE 2: This updating method will only work for non-BES BlackBerry users. Any BIS users out there, please post a comment and let us know if the update works, and which device you are using!
UPDATE: Looks like BlackBerry 8330 users are still out of luck. Sorry guys! (Thanks, Nan)
Oh sweet glorious day! There have been a variety of BlackBerry Nation members who have been suffering through news about new BlackBerrys and OS 5.0 features, when all they want is OS 4.5 to be released by their carrier. Wait no more: http://www.BlackBerry.com/Upgrades is now live, allowing you to upgrade your OS directly from RIM.
You’ll need to use Internet Explorer and click “UPGRADE NOW” to download the 25MB ActiveX control which is essentially a watered down version of Desktop Manager. At the end of the process you can enter in your email address to be notified of any future OS upgrades.
Note: If you had already installed another carrier’s version of OS 4.5, you’re going to have to downgrade to a lower OS version before installing the proper one (thanks Al).