This thread is uncharacteristically unhelpful. I will do what I can to give you some advice as a long-time windows-users (and linux and VMS and every other OS under-the-sun).
The situation is this:
Powerbooks have just been updated for the first time since last January. That means that the PBs currently available are as good as they're going to get for at least a few months, and probably longer.
The current PBs (and iBooks) are powered by the Motorola G4 proc. (they didn't get the Freescale 7448s into the latest revs, much to my disappointment). The G4 is now a pretty old CPU, and the Pentium M is unquestionably superior. Nonetheless, the current PBs (and iBooks) are very nice systems. 'System' is the key word here. To use the well-worn 'car' analogy, a corvette has a much more powerful engine than a porsche, but a porsche is generally a better car because all of the components are well-designed to work together as a system (chassis, suspension, breaks, steering, engine, etc.). The PB is like a Porsche. It may not be the fastest machine on the quarter mile, but it handles very well overall. And it is priced accordingly.
Sometime next year new PBs will come out with Intel CPUs (probably Yonahs, maybe Memroms) that will be seriously fast. If you can wait, wait. If you need something now, the current PBs are more than fast enough (although they aren't the fastest) and they are very well-made and well-designed. I just ordered one myself.
But WRT computers, waiting always gets you more bang-for-your-buck. On the other hand, what does waiting cost you?
And with respect to your concern about switching to Mac OS, I wouldn't worry about it. After considerably more than 10 years using windows and other OSes, it took me about 15 minutes to get comfortable with OS X, and about two weeks to feel totally at home with it. OS X is by far the best operating system I have ever used (having started with a PDP-11 in 1968) and is still way ahead of anything Microsoft has planned for Vista. You'll love it.
Cheers
