I have also been thinking about picking one up, I have seen g4 ibooks going for pretty cheap like this one:
http://cgi.ebay.com/Apple-iBook-G4-...89009585?pt=Apple_Laptops&hash=item19bf9e5eb1 I disagree with everyone, I have had mostly good experiences with ebay. also if someone sells you a broken ibook you can just make a paypal claim to get your money back.
be careful there if someone sells it private (and not from a ebayshop)and sells it as "used" you wont stand a single chance if it comes full of scratches , as long as it matches the description at the time you did bid or pressed by it now ,as it is listed as "used ", which includes signs of wear so the seller does not have to point out the deep scratch or the cracked broken edge , fair if he does but.... he does not have to ,listing as "usual signs of wear" is enough, as he can always point out that other iBooks sold on ebay have scratches and cracks too so it is a usual condition
and be especially careful( as it happened to me , not on a iBook but on a iMac G5 ) when you ask questions ,the seller might quietly remove or add things from the listing ,so always read again and again the listing before you press buy it now or bid , dont assume that the listing you did read a minute ago is still the same after (in case of a iBook) you asked for example if there had been any problems for example bad soldering ,or if the battery gets charged a simple add on to their listing can make your chances zero of getting even from paypal something back, for example if he adds to his formerly listing
" cant give warranties on hardware"
you are out of luck even if it stops working a day later