Why switch to Debian? It's not like his customization does transform it into a radically different distro. For one thing, he keeps the Ubuntu repos (which I personally find better on a Desktop).

Good question - and I have no answer. Im just too used to ubuntu and all the default repositories, etc.

However, I primarily intended this setup for someone like me - who sets up a default ubuntu install and then finds himself slowed down. So these steps are intended to be run safely from a fully working ubuntu install.