I think what most people are not even considering that will make a huge difference depending on what you do and with future versions of the Mac OS is the amount of ram the ibook max's out at. 640MB pretty much turns the ibook into a disposable computer for many folks much earlier than they would like. I actually consider that to be the biggest issue with the ibook. When they deliver a G4 or higher performing G3 based system, I hope this gets addressed.
Besides more memory makes things easier on battery life since you don't need to hit the swap file as much.
Besides more memory makes things easier on battery life since you don't need to hit the swap file as much.