Expect to be Horrified
Well... I have a friend who has an original iBook. If it still has the original hard drive, then OSX will literally fill the entire hard disk. It will also be very slow and you'll pretty much be only able to surf the web, instant message, email, that sort of thing. For that type of usage it would be usable. For anything else... run OS9. Also, I do believe you can actually install more RAM than Apple's quoted max.