The other day, I decided to take my computers down for the few hours it would take to upgrade to Hardy Heron. I wanted to take advantages of the new features and the improved Firefox 3. So far everyone is working very well. The upgrades went perfect, except for two issues, one on each computer.
First off, on my laptop, the host name of the computer fell out of the host file so sudo couldn’t work. This was almost a major issue, but it is very easy to fix.
Go to System-Network-General. Click on the unlock and enter your password. Next, copy that hostname listed there.

Next, go to hosts tab and you are going to want to add the hostname localhost at ip 127.0.0.1 and the host name from the previous step at ip 127.0.1.1 . Basically, get it looking like this screenshot.

After you finish, reboot your computer and you are back in business.
The second problem that I encountered was on my desktop. On its first reboot, it had several crash errors. I rebooted and they didn’t appear again and haven’t since. I think it’s just some legacy tracking errors.
All in all, I like the performance I am getting with the new Ubuntu.