In order to play World of Warcraft smoothly on PowerBook or iBook, you need to tweak the configuration a little bit to get the best results.
Besides basic system requirement, I suggest you have at least 512+256M RAM. I have 1.25G myself and no problem at all, if just talking about memory.
So you need to configure it according to the screenshot.
If you have at least 64M RAM for you video card, and at least 1G RAM for your system, you can actually turn Terrain Texture and Texture Detail to HIGH. This will reduce your FPS a little but not much.
With this configuration, and my machine is a 12″ PowerBook, I can usually get about 30 fps in the field, which is almost an enjoyable FPS. In the city it could be less than 10 fps but as the characters are loaded, it will get better.
Anyway you can tweak it as you want to. But this is a configuration which works for me well.
