The jury is still out on the Unity desktop for me. I certainly didn’t need to switch away from Gnome, but I’m a long time supporter of Ubuntu so I’m giving it a go. But when I was messing around trying to get a PS3 SixAxis controller working with Portal 2 today I managed to make the sidebar and panel disappear. What’s more, Alt-F2 wasn’t bringing up the run command dialog. Luckily I had Guake running so I was able to use the virtual terminal.
Now if you search around, a lot of folks will tell you to run “unity –replace”. This made the windows jump around but didn’t fix the problem. On Lucid I would have restarted Gnome, calling the gdm daemon to restart. But there’s no gdm here. I searched around on that topic and found that gdm has been replaced by lightdm. So, if you hose your Ubuntu 11.10 desktop UI and need to reset it (without rebooting) use this new command:
sudo service lightdm restart
I hope this is helpful!