I'll just replace the ibook for the powerbook G4

If you're already using a Mac and are happy with it, I cannot come up with a compelling reason to get a PC laptop at all. You've already come to this conclusion, but I thought I'd reinforce it.

Specifically, you strike me as not being inclined to enjoy arguing with a computer, and Macs do a lot better at ``just working'' than PCs do, especially, in my experience, with laptops.

Also, it narrows your choices down quite a bit. There's only five to choose from. Of course, there are options for each, but that would be the case no matter what you chose.