I pulled mine apart and threw an 80GB drive in it. Problem is that I cannot install any OS to it or even restore from the restore disks. The installation always craps out right at the very end with some random error and while I can see a blessed System Folder, the clamshell refuses to boot from it. It has also developed an error where the system does not recognise double clicks so I have to open apps from the menu.
Also when ripping it apart I noticed for the first time the lack of fans and the thinnest of heatsinks for the three chips. That did surprise me. If I can sort out the OF issue and get an install going I shall invest in an SSD and have a silent notebook.
On the plus side, the battery charged right up. Not bad for an original.
[edit] I think I have cracked the OF problem. Seems like the keyboard membrane needs a good spring clean. I popped the upper cover off and used external peripherals. OF accessed, OS9.2 installed, albeit not without complaining, and firmware updated - I had to replace the cover for that. Could not get the iBook to access the firmware updater from pressing on the contacts and an external keyboard.
Cannot do too much until I get more RAM for this. Will leave the keyboard clean for a very rainy day. Looks like a very fiddly and delicate job. I have managed to get double clicks recognised again but I reckon it is still sending ghost keypresses to the system. Sleep isn't working - it seems as if the optical drive is waking it immediately or it may be the dirty keyboard. That is for later to sort out.
Naked clamshell below. Those of a nervous disposition may wish to look away.