One of the users on Modaco Forum rooted Nexus One before it was even released. In forum he describes how to root Nexus One in Linux Windows And Mac he also provided boot.img (Image File) called SuperBoot that will root upcoming Google Phone which is expected to be released on January 5th.
People have sometimes too much time on their hand 
but I am sure he was bored and wanted to have his 15 minutes of fame or few years jail time if Google get’s pissed off.
Anyway, with rooted Nexus One you can pretty much do same thing what you could do on regular Android OS and that is install Apps directly to your SD card or things like I did for example: Installed Debian OS (Linux) on my G1, yeah I know it’s all cool and dandy but all the hassle after each Firmware Upgrade, I don’t see any reason to root my G1 anymore.
More Info from others via Techmeme
