All I can tell you is that if you go with the Mac you will not be disappointed. i was in your shoes less than a month ago when I was one step away from buying an HP. My advice (from a lifetime Windows user) is to take a look at both computers (side by side for a real dramatic effect) and, no question about it, you will pick the Apple. Powerbooks are quality machines, easy and a joy to use! I have had mine for only 2 days and am absolutely amazed.
First off if you will be listening to any music, or doing any kind of photo editing, iTunes and iPhoto can't be beat. With iTunes its a breeze to import songs from your favorite CDs to your Powerbook, or simply just play a song while watching the visualizer.
iPhoto is very easy to use. I love my digital camera but the software it came with was horrible. I can't tell you how many hours I spent trying to install it on my PC initially and many random times after when XP claimed it "didn't recognize the device." With my PB, it couldn't be any easier! I simply plug in my camera (no software required!!) and iPhoto recognizes my pictures. My favorite feature is the slideshow which plays photos in my albums synced to my favorite songs.
I've watched tons of DVDs on my PB simply because the crystal clear screen makes them a joy to re experience.
I just ordered Office 2004 so I can get some more *ahem* productive work done. And if, like me, you'll be doing a lot of typing, the PB keyboard is very comfortable (and the backlit feature is just so cool). I don't even mind the trackpad (with only one button!

) which I thought I would hate.
The thing that makes the most difference is that the people at Apple pay attention to details. I've never had a computer where I've been almost hypnotized by the screensavers!
Go with the Powerbook and you'll never be disappointed!
Good Luck