I find the keyboard is great! The iBook keyboard is the same as the powerbook keyboard except for the materials, and the powerbook keys are are a little more sculpted. That said, this is by far the best laptop keyboard I've ever used. I can touch type full speed on this keyboard, no problem; and ergonomically it is one of the few laptop keyboards I've used that I can type on for long periods of time.
(Note that all apple laptops have the same size keyboard, so my 15" keyboard is not any bigger than the 12" ibook kb).