On a clean install of Ubuntu 10.04 and 10.10, you may find that using vi to edit any file may not work well.
Hitting i may not display “INSERT” at the bottom of the screen, hitting the arrow keys may only cause A, B, C, or D to be typed on the screen (instead of actually moving the cursor), etc.
To get it to work more like you’re expecting, open a terminal and type this:
echo set nocompatible >> ~/.vimrc