This mod reminds me on a few PC mods I did in the past with a CF card. Most CF cards are faster then HDs. They move as fast as the controller can let it. Unless you're running a system with ATA100 and the drive is also ATA100 then there wouldn't be a diffrents.

You can fit on a small copy of OSx onto a 2GB partition. I had my iBook running with it but it crashed after installing a few programs that screwed up the startup. Beleve it or not half of the stuff in OSx you don't really need. Just run the delocalizer program and remove a lot of programs you don't need. After that you can remove a lot of files that Apple tossed in that depend on UNIX software that isn't in use. Also you can remove alot of Frameworks, PrivateFrameworks and Services. Also you can remove a few things from /bin, /sbin, /usr/bin, /usr/sbin, /etc, /usr/etc. I wish I still had the kill list I made for files you didn't need for OSx.

Thing is this makes OSx so bare it would be like one of thoses Linux Live CDs.
To live is to let die