Ubuntu 9.04 released at April 23,and include many new features since ubuntu 8.10
ubuntu 9.04 include the latest gnome 2.26 desktop environment with many new features.
2.X.Org server 1.6
The latest X.Org server available in Jaunty is version 1.6
3.Wacom tablet hotplugging
Wacom tablets now are enabled automatically when attached, no longer requiring xorg.conf modification
4.Ext4 file system support
you can select ext4 for your file system when you install ubuntu 9.04 with a live CD.
Jaunty also includes many other new features such as :
Linux kernel 2.6.28 Boot performance New style for notifications and notification preferences Cloud computing
For more about ubuntu 9.04,please refer to http://www.ubuntu.com/getubuntu/releasenotes/904overview