After the update, I had to do a little house cleaning. OpenOffice.org was still installed even though LibreOffice is the new office suite. There were a few other packages still installed as well. In total, I removed 152 MB of unused packages after the update.
This is the first release to use the Unity desktop environment by default. Gnome has always been the default desktop environment for Ubuntu. I've been a big fan of Gnome, and I was not too excited when Canonical announced that Unity was going to replace Gnome as the default. With that said, after using Unity, I think it's a solid desktop environment. It has a lot of usability improvements over Gnome 2. I'm really interested how it will compare to Gnome 3.
Unity isn't all good, however. I have a few complaints, but first, a disclaimer: I am running an alpha version of the software, thus some of the problems I experience may be fixed before the final release. Also, I have been a Gnome user for 6+ years. Some of the complaints I have could be due to my inexperience with Unity.
Now my complaints –
First, I have always used focus-follows-mouse (not focus-and-raise-follows mouse – that's annoying). Unity uses a global menu (similar to OS X). This means that the File, Edit, View, etc. menus appear at the top of the screen instead of the top of the window. With a global menu, the mouse has to leave the window on the way to the file menu. This means the window loses focus and therefore causes the global menu to change to whatever window now has focus. I know that I'm in the minority for my preference for focus-follows-mouse, but the global menu makes it nearly impossible to keep this option enabled. Bye-bye focus-follows-mouse. Tear.
Second, Unity doesn't seem as customizable as Gnome. I cannot add any applets to the panel or the launcher. I can pin apps to the launcher, but that's about it. There are some icons on the launcher by default ("Files & Folders" and "Applications") that I want to remove, but right clicking on them or dragging them off the launcher do nothing. I hope that the apparent lack of customization is just due to my lack of experience.
Last, there are a few bugs I've noticed. When displaying all applications in the menu, no icons are displayed. Dropbox's icon is not in the indicator applet. I cannot close KeePass 2.x (a mono application). When attempting to do so, the screen goes black for a second and KeePass is still open. I'm sure these issues will get resolved before the final release (especially if I file a bug report).
I've frequently upgraded Ubuntu during the alpha and beta releases. For the amount of changes being introduced in this version of Ubuntu, there is surprisingly little instability in this alpha release. There are a few bugs, but I'm looking forward to the bug fixes and overall polish that will be developed over the next month leading up to the final release. If you're impatient like me, upgrade to the alpha, but if you don't want to risk instability wait until the final release. Either way, Natty Narwhal is looking like a great release.