HTC is on a bit of a Windows Mobile 6.1 upgrade spree. After the Telus HTC S640 and HTC Touch Cruise upgrades (only to mention the last two), the latest HTC device to get the upgrade is the HTC Touch Dual.
According to the reference page, the firmware only includes Windows Mobile 6.1 Professional and makes no mention of any other enhancements and bug fixes.
Note: The update will replace the current ROM image and will erase partnership and all user data and programs on your device. Be sure to back everything up before you start.