The grand unified bootloader (grub) not being updated since 2006 Canonical announced to release the next Ubuntu version 9.10 - also known as "Karmic Koala" - with grub2 as the default boot manager. Of course I got curious and as I read an article in c't about this topic I had to see what grub2 was about!
If you're running Ubuntu 9.04 Jaunty it's quite easy to switch to grub2. However, if you installed Jaunty to boot from an ext4 partition you're likely to have grub2 installed already.
There is a nice howto which explains installing grub2 in Jaunty at Ubuntu's wiki here. If you follow the instructions, grub2 will end up in your boot partition (not the MBR) first and a new entry to your old grub is added, giving you the chance to boot grub2 via chainloader. You are advised to follow these instructions, because if grub2 doesn't work for you, you're still able to boot with grub. However, I decided skip this step and installed grub2 straight to MBR.
CAUTION: fiddling around with the bootmanager may leave you're system unbootable!! If you don't know how to recover from such a state, please don't do it!