The iBook 12 inch is great value for the hardware you are getting. The powerbook, is not so much. However the powerbook is priced more or less at a similar price to windows 12.1 inch laptops (atleast here in Holland). Its a nice, well built sexy machine (both powerbook and iBook). But your problem, as has been pointed out by other posters above, is software. However, you could get your hands on Virtual PC, and your mac will run any windows programs like it were a windows laptop . This is an extra expense that may increase your initial purchase costs of the laptop to over what similar spec'd windows based latops offer.
I too have been thinking of the apple alternative for some time now and have read such threads on many websites before. The stability issue - windows XP is FAR more stable than anyother windows OS, the mac OS DOES crash occasionally, Id say because of the closer harmony between hardware and OS on macs its stability may have a slight edge over Windows XP, but its only slight. The problem is not so much the OS noww, its the badly written programs. Battery life is better on the macs, no contest. Forget the nonsense people say about Dothan chips, they can get you going for 3-6 hours max. Macs get you going for 6-9 hrs (especially if you are a light user). To give you an example, I have classes all day at university, and two of my friends have laptops they use all day - one apple iBook G4, one IBM thinkpad R50 (Dothan). they pretty much use the laptops the same way the whole of the day (to take lecture notes etc). The iBook at the end of the day still has some (minimal) battery left, however the Thinkpad needs recharging during the day. Both laptops are only a month old and use batteries supplied by the manufacturer at time of purchase and both have 14.1 inch screens.
So really the only reason left for me not to purchase an apple is
1)Speed - I've heard mixed reviews about its performance.
2)OS - learning the new OS takes time (even if its easy). Especially if you are fully used to windows.
3)one button mouse. Why apple? why dont they just give in, and use two???
4)Upgradeability - upgrading the harddrive on mac can be tricky I've heard. Could be just a rumour.
5)gaming. (but the original poster wasnt interested in this so I wont laborate).
Maybe theres a few others, but in the end, its a personal choice. I recommend you check out the apple's keyboard and OS at a shop near you. If you like it, buy it,as there not much you are losing by abandoning windows.