BlackBerry OS 4.5 is now available for the T-Mobile BlackBerry Curve. Specifically, the upgrade will give you version 4.5.0.81.
The latest version of the BlackBerry OS comes with quite a few enhancements, including an updated user interface, an improved HTML email layout, Bluetooth A2DP, and more.
Note: Be sure to back up your data before doing the upgrade. The BlackBerry Desktop Manager comes with an option to Back up device data automatically during the
installation process. You’ll find more information in the upgrade instructions.