Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
I can confirm for you that PC2700 WILL work inside a 1.0 GHz iBook. I had 1.25 GB of PC2700 for a number of years and it was fine. Just make sure it is SO-DIMM.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.