I thought I'd share here some of the trials and tribulations I experienced in last night's upgrade to Ubuntu 11.04, Natty Narwhal.
Using the flgrx driver most of my desktop was black, with occasional bits of the background visible. I solved this by selecting "Classic Session" at the GDM prompt and following the instructions at http://ubuntuforums.org/showpost.php?p=10618166&postcount=1 and https://wiki.ubuntu.com/DesktopExperienceTeam/UnityWithFglrxBeta
In short:
Enable restricted in your apt sources list
and
sudo apt-add-repository ppa://unity/daily
Then:
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install fglrx
sudo update-alternatives --config gl_conf (and select the line with fglrx)
sudo update-initramfs -u
Reboot.
I received errors from Adobe AIR/Tweetdeck saying the secure storage system was out of action. I solved this by using the instructions at http://kb2.adobe.com/cps/492/cpsid_49267.html:
rm -rf ~/.appdata/Adobe/AIR/ELS
You'll have to re-enter your account details.
I reported this as a bug in Thunderbird, because that's where I first noticed it (https://bugs.launchpad.net/ubuntu/+source/thunderbird/+bug/751067), but it actually seems to affect every application, but only in certain places, most specifically in the display of PNG files. Basically, some of my colours are really messed up. This could be because of the experimental flgrx driver, but time will tell.
To not be entirely negative... I love Unity! Have so much more space available on my desktop to do my actual work although, in its present state, the entire system feels very sluggish compared to traditional Gnome.