Notebooks typically have lousy ergonomics and the iBook, by dint of its design, can't overcome this. But Apple portables rate far better than their competitors in this category as far as I'm concerned. The trackpad - well, the Titanium pinched that idea from the iBook. Big and wide, smooth and metallic, the iBook's trackpad is gives good pointer feedback. But you either like or hate trackpads and, by all means, go ahead and plug in a USB mouse.
Keyboards are inherently personal things as well.
Stick the owners of a dozen PowerBook models in one room and each one will swear their model has the best one. The 2400's is good, but I can't type for toffee on small keys. But it's a personal preference, that's all. Again, the iBook limits your choices. One keyboard fits all.