Mmm, found this. Is that all?

http://www.tabletpcreview.com/default.asp?newsID=1171

* A change in the email client from the current one to a version code-named Modest
* Tweaks to the microB web browser. However, the rendering engine will still remain the same as Firefox 3 Alpha 1, just as the current version has
* An improved network switcher that will facilitate handing off connections from Wi-Fi to WiMax and vice versa
* Improvements in the finger-UI performance and launching
* A several enhancements to system libraries to improve performance and speed.

Diablo will run almost all of the same programs as the current operating system (OS2008, code named Chinook). However, there will be different repositories for those that choose not to update to Diablo in order to minimize confusion about application compatibility.