I recently bought a macbook after my dell laptop called it quits, and I am 110% satisfied with my decision!!! I've been a mac user for a couple of years now, and quite honestly, I forsee myself staying part of the family.
If you are simply buying a laptop for basic word processing applications and internet, you can't really go wrong with buying a $600 laptop from dell. However, if cost is not an issue, I would seriously recommend the macbook because it's more of an "experience". There's nothing quite like the feeling of knowing you've wasted hours of your life tooling around with addictive programs like iPhoto, iWeb, iMovie, Garageband, and iTunes
A majority of my gradwork is research based, so I'm no stranger to powerpoint, word, and photoshop. I feel that these programs actually run better, and are easier to control, in the mac atmosphere. I really don't know how to explain it, but once you use it, you'll understand.
But before you decide to make the switch, make sure you know what you are getting yourself into. Don't be one of the people who buys a mac and bitches all day about not having the second mouse button...