Since buying my (second hand) PowerBook earlier in the year I've been really impressed with it - I use it far more often than I use my Intel based MacBook and if I had to give one up the PowerBook would be the one I'd keep. I know it's slower and more and more software isn't available for it (due to it being PowerPC, er, powered) but the construction of it is so tidy with all its aluminium, the battery still lasts around 4 hours and everything works as it should. But mostly it's the size - I've got one of the final 12" models to be built so not only is it small and light it also packs the fastest PPC processor Apple ever put into a 12" model complete with DVD burner and decent (for 2005) nVidia graphics.
Not only does this laptop get carted around when I'm on call (being small and light is a massive bonus here and the reason my work supplied ThinkPad sits at home unloved most of the time) I've also started playing games on it - nothing fancy mind you but I'm impressed at how many of my old PC game titles run on it (things like StarCraft, Diablo II etc all run off the same install CDs), and I've since bought other early-to-mid 2000's titles such as Halo and American McGee's Alice second hand off ebay.
Yup - things are pretty much perfect with this machine... Until Apple released the new MacBook Air last month. Suddenly I want (no, I *need*) a new laptop, an 11" Air would be brilliant. The 13" MacBook Pro was never really a replacement for the PowerBook 12" (despite what people were saying when it was first released), it was simply too big. Now with the new Air however...
I'm off to check on my bank balance and start on excuses on why I need one of these.