If you switch from your PowerBook to a MacBook, here are...
- more raw processor power
- built-in camera
- magnetic latch, power cable
- scrolling touchpad (you might have that already)
- very compact form factor
- glossy screen
- plastic shell
- lower screen resolution
- Office for Mac does not run at native speed (yet)
- less RAM (Macbook has no dedicated VRAM, so you need to factor in 64+ MB for that)
- lower 3D performance...