OS2008 Feature Upgrade v. 4.2008.23-14 includes:

Seamless software update
After flashing this OS2008 Feature Upgrade further OS updates will be made available over-the-air. User will get notification about the availability of OS update in statusbar automatically when new updates are provided. This works only over WLAN connections. It is also possible to check for updates manually from Application manager.

The updated email application now supports simplified account setup and presets for various service providers.

Support for Chinese character rendering in Email, Browser and RSS feed reader.

Other improvements

In relation to OS2008 v. 2.2007.51-3 there are numerous issues fixed all over the operating system including updated openssl. Smaller improvements have also been introduced to several areas such improved browser panning performance.