New software, new features, new bugs.
Here are some of my problems, and some workarounds. More will follow. Maybe.
You might also want to have a look at the Ubuntu 8.04 Release Notes

I was surprised this time. No major problems with my X800 XL graphics card using fglrx. I just did

sudo dpkg-reconfigure -phigh xserver-xorg
xrandr --output DVI-0 --auto --right-of VGA-0

and Dual Head was working again. Sometimes even the Screen Resolution tool lets me configure dual head properly.

The Tilda crash bug is fixed now. But there is another one: It looses focus after opening. There are two workarounds for this:

1. For Compiz users: http://ubuntuforums.org/showthread.php?t=530764
2. All others have to open tilda twice everytime they want to use it. There is a hack that does this for you, but i don't even want to talk about such an ugly hack (ssshh: it has to do with xbindkey, xautomation and .xbindkeysrc).

You may also want to have a look at this: Hotkey to switch Keyboard Layout. There is at least one bug that prevents you from switching the keyboard layout. If this happens, here is how to get it working again: Just delete the second keyboard layout in the Keyboard Preferences dialog and add it again.