I swear I type my life story roughly 4 times a day here on MR.
I owned a 12" 1.33GHz PB for about a year then got a more powerful desktop iMac G5 and no longer needed the 'power' of my PB. Offered it to my older sister in exchange for a new 12" 1.33GHz iBook.
Yes I prefer the sleekness/ small/ slimmer compact form of the PB as well as its keyboard.
However, I love the fact that the iBook feels like it could take a beating and still look nice. Love the MUCH better wi-fi reception. Love the MUCH MUCH better battery life (roughly 6+ hours vs my PBs 4+ hours). Love the fact that the iBook only gets warm while my PB would get uncomfortably hot.
And truth be told, in my backpack, the weight difference is practically negligible. Also, the slight difference in front BUS (or whatever that thingiemajig is) doesn't make in impact for me and my simple needs in a laptop.
In short, I have grown to truly love my iBook and wouldn't trade it back for my PB (although, I feel a slight pang because I hate how most people will assume that a woman uses the iBook because she doesn't understand that the PB is the higher range or doesn't need a higher powered machine).