Like hondagus87 said, it really depends on what you want to do with it. I've been a Mac user since '01 and have had a ton of different machines, all for different uses. I have had towers, all-in-ones and notebooks, depending on my needs at the time. Right now, since I'm primarily a student again, I've got my precious MacBook 2.16GHz C2D (White - I didn't feel the need to pay the BlackTax. ^_~)
Whatcha want it to DO?