I would recommend against using this plugin. This was deliberately left out of core. In fact, we even took the extra step of also hiding Tools > Network unless a constant was defined. (Background: I wrote most of the Tools > Network process that you duplicated and extended here.)
Very simply, Multisite is not for the faint of heart. Forcing manual changes to install Multisite is on purpose because it requires a lot of server configuration to get it right. If you don’t know how to add constants and follow the instructions at Create A Network WordPress Codex, then chances are you should not be running Multisite in version 3.0.
I installed a network probably 500 times during the course of testing. If you know what you’re doing, it takes 3 minutes. If you don’t, chances are you shouldn’t be using it.
He of course is referring to: Wordpress Multi-Site Enabler Plugin JG Web Development
I don't know what to think about such face slappery...