I second the motion (MacBook). You can run both Mac OS X and Win XP SP 2. I have a Mac Mini (Intel) that is triple boot - OSX, Win XP and Linux (Fedora Core 6).
I plan on getting the MacBook sometime this Summer.
I love my BlackBook. 2GB RAM.
(For the uninitiated: That’s a black MacBook.)
If you’ve got the bux, the MacBook Pro is even better.