I've been using my first gen Macbook Pro(1,1) for 2.5 years now and have had very few issues.
It's survived several falls to the ground, both onto tile and carpet, from lap height, to kitchen table height. It's only suffered bumps and bruises and still running very strong. My only complaint is my 100GB HD(which I'll be replacing with a 320GB one soon), and my limit of 2GB of RAM. And the only time that bothers me is when I'm running Firefox, Adium, iTunes, and Photoshop at the same time, or running a virtual machine in VMWare.
I imagine I'll keep it until I'm out of college at the very least, but probably longer than that. The longevity of Apple product is amazing, my girlfriend runs a G3 clamshell all maxed out with no issues, and I've also got a Powermac G4 that I use regularly as well, and those are both coming up on being 10 years old.