My transition to Ubuntu 8.04 (Conclusion)

Xfce

As for now I'm running Ubuntu on my not too young T40 Thinkpad, I am using the xfce desktop environment. It proved faster than gnome (which seems to have become better with 8.04, though) and I like the xfce panels better.

Compiz

I described in another post how I got compiz running on my old and unsopported ATI Mobility 7500. All it needed was some sieving of ubuntuforums.org. I would have liked a commandline option to force compiz to start without checks and a more informative comment, why compiz wouldn't start, but for any user who would risk using compiz on unsupported hardware it shouldn't be too hard to find the solution. As far as I think, it's too bad, ATI doesn't provide linux drivers for their old hardware.
Another point was, that the compiz-settings from 7.10 didn't seem to work under 8.04 (especially the window-rules in the animation settings). The solution was to click the default setting buttons, apply and re-insert the rules from before. That's considered a bug, and will be corrected, I think.

More

The applets have become more userfriendly. The nm-applet, for instance, launches the network-admin application without the usual gksudo password dialog. If you need, you can unlock it with a button. The Edit Wireless Networks-option, which let's you edit the preferences for all known networks used in DHCP mode, is well done. There is a small icon in the tray to safely unmount removable drives and media. The CPU graph applet (xfce) is much improved and launches the top command in a terminal as default on leftclick.
A lot of the software is updated, a major libc update found place, to let packages like flightgear-1.0 finaly find their way to Ubuntu.
My overall sensation is, that everything is a bit more tidy, neat and grown up.

Problems

All together I experienced no major problems (other than those mentioned above). Some minor things were corrected by reinstalling the according software packages or mostly resetting some preferences.

Conclusion

Considering, that I run linux on a heavily unsupported platform (not the Thinkpad itself, but my broadcom wireless and ATI graphics cards), in retrospect, the update process felt less risky than a Windows XP service pack installation. Much less!
If you don't mind fiddling with some settings, just do the upgrade. If you do, read the Ubuntu forums, check for problems with your hardware and wait for the moment it feels safe enough to make the change (maybe wait for 8.10). Since Ubuntu 8 is a long time support version, it should be worth a wait.