I've got a 15" 1.67Ghz Powerbook with superdrive and I love it! There's so many things I can do on my mac.
I've never really used a PC laptop, but the PowerBook has a very decent battery life for the size of the screen, and the performance it offers. Wireless networking can be a bit temperamental, but at close range to the WAP it works fine. Home networking is a breeze, I plug my laptop into my home or girlfriends wired network, and it works straight off the bat, unlike some Windows laptops where its taken us an hour to get working.
Only con about the powerbook that I've found is that the case is a little soft, and if you drop it and it hits a corner, as it did mine, it will dint - but all the components work still, so its very strong.
Also, dont let the Processor speed influence you on performance. The 1.67Ghz PowerPC chip from IBM is on a different architecture to the ones from Intel and AMD, and I've heard that the G4 found in the iBooks and PowerBooks (and mac minis) can be up to twice as fast anything from Intel - but I think thats a bit over the top. The Ghz's are significantly lower Vs the power you get from them, compared to the Ghz vs Power on an Intel machine.