After upgrading to Ubuntu 11.04 I ran into a number of "issues" some more critical than others.  The following is a collection of issues and fixes that I have applied as I discover them.  FYI: I currently hate Unity but I am trying to give it a chance - but it is painful.

Blank Screen on Boot

When rebooting for the first time after upgrade I had just a blank screen and no way to proceed.  In short, the issue is with plymouth and luks (cryptsetup) when it requires you to enter in your passphrase. The easiest solution I have found, and I tried many, was to add GRUB_GFXPAYLOAD_LINUX="text" to /etc/default/grub and the rebuild grub with the "sudo upgrade-grub" command.  The essentially disables the graphical plymouth and gives you a working text interface.  It appears that this may be still be a bug that is being worked on but there is no current fix that I have found as of this writing.

Dropbox System Tray Icon in Unity

Dropbox was running but the tray icon was missing.  In order to get it back I had to upgrade the dropbox daemon

dropbox stop

rm -rf ~/.dropbox-dist

dropbox start -i

Change Default Login to Gnome instead of Unity

I am not loving Unity at all.  I am trying to get familiar with it on my desktop but my laptop is another story. The change is simple.  When logging in simply select your user account and change the default login (bottom of page) from Ubuntu to Ubuntu Classic.  After that it will store your default on future logins.

No systray icon for application

This is actually a problem with a lot of apps.  As it turns out the Ubuntu folks want apps to be redesigned and a lot of apps won't work with the systray unless added to the whitelist.  To do this you can first look at the existing whitelist

gsettings get com.canonical.Unity.Panel systray-whitelist

To add another application to the whitelist you must include the existing string from the output above and add your app at the end.  In my example I will add keepassx (although keepassx has other issues preventing this from working)

$ gsettings get com.canonical.Unity.Panel systray-whitelist

['JavaEmbeddedFrame', 'Mumble', 'Wine', 'Skype', 'hp-systray']

$ gsettings set com.canonical.Unity.Panel systray-whitelist "['JavaEmbeddedFrame', 'Mumble', 'Wine', 'Skype', 'hp-systray', 'keepassx']"

Non-responsive Left Edge Reveal for Unity launcher

I run synergy with my laptop set for the left of my main desktop screen.  This is not a good combination with the default for the unity launcher.  In order to address this I had to open CompizConfigSettings Manager (sudo apt-get install compizconfig-settings-manager), Search for Unity, select Ubuntu Unity Plugin, and change Reveal Mode to TopLeft.

Systray Icons not showing up after login

If you have configured the whitelist and applications aren't showing up in the applist it is likely because they are loading before Unity which causes problems.  To address this you must modify the exec command in the autostart file either via the command line (~/.config/autostart/app.desktop) or using the Startup Applications app.  Change the exec line to read

bash -c "sleep 15; x"

Replace x with whatever the default exec line was before (ie: skype)

Disable Recently Documents in Launcher

I hate recently used lists in anything and am annoyed when there is no obvious way to do this.  In the Unity Launcher you must

echo -n > ~/.local/share/recently-used.xbel && sudo chattr +i ~/.local/share/recently-used.xbel

rm ~/.local/share/zeitgeist/activity.sqlite

zeitgeist-daemon --replace

Additional Unity Information

I am a long way from loving Unity but I did find a link that proves to be an interesting read:

http://castrojo.tumblr.com/post/4795149014/the-power-users-guide-to-unity