I wouldn't pay the current price for the 12" PB -- a soon to be outdated machine.
I've had the 12", 15", and 17" PB's over the years; the 12" PB just feels claustrophobic: its lack of screen space, overall dim screen quality, bad sound, etc. sure, it's small, but so is the iBook, and you'll save a lot more with the latter.
Get the 15"PB if you can afford it or hold off until MWSF.