As requested, this is the fastest way I have found to rename the XO.
1.Open up the developer console (Alt-= on mine,may be different on others)
2.Go to the terminal
3.Open the file ~/.sugar/default/config with your favorite CLI text editor
4. Find the line that says nickname and edit to it your liking.
5.Restart sugar (ctrl-alt-backspace) or restart the computer
6.Voila, the laptop is now renamed!