Screen is like a window manager for your console. It will allow you to keep multiple terminal sessions running and easily switch between them. It also protects you from disconnection, because the screen session doesn’t end when you get disconnected.
If you install Ubuntu from a cd-rom, when you try to use apt-get to install new software it will prompt you for the cdrom every time. Kinda frustrating!
Ubuntu Server has the native ability to run multiple console sessions from the server console prompt. If you are working on the actual console and are waiting for a long running command to finish, there’s no reason why you have to sit and wait… you can just open another console and keep working.
When you are on the Ubuntu server console, you will invariably run commands that scroll past too far to see them on the screen. Since you aren’t in X, there’s no scrollbar for you to use to look back.
If the Ubuntu Server installer has set your server to use DHCP, you will want to change it to a static IP address so that people can actually use it.
If you’ve installed your Ubuntu installation with DHCP, it’s really easy to reconfigure your system to use a static IP address with the GUI based Network Settings dialog.
Ubuntu has a trash can/recycle bin feature similar to windows. The difference with Ubuntu is that you can empty the trash from the command line.