Yep, my girlfriend is on a 333mHz running 10.3 right behind me.
The only way I was able to get it to work is to clone the harddrive from an iBook that had 10.3 installed on it and got put out of service. Popped the cloned HD in, and it booted right up. I'm sure just using the installer discs will work, it just wouldn't for me, it yielded kernel panics.
Have fun!