I have installed Lion as an upgrade (and copied off the installer to an external HDD). The Emergency disk partition is there - and I assume it works.
Apart from backing up essential data; is there anything I should be aware of if I want to do a fresh install of Lion by erasing the HDD with the system on it and then booting from the Emergency partition?
To answer my own question a bit further. The following two links both show how to install Lion without the need to first have Snow Leopard installed.