It's not the best machine you can afford though for a lot of people. I have a X200 thinkpad at 12" which is 600 grams more than the 11" and 300 grams more than the 13". But it has a dual core i5 at 2.5 gigahertz which is a fair bit faster than low clocked cpus of a generation that was released in 2006, 4 gigs of ram (rather than 2) and an Intel 80gig SSD running Ubuntu 10.10. The battery is 7 to 11 hours. With their batteries in it it'd be even lighter than it is, most of the difference is right there. It already has an app store with nearly a 100/0 free/paid split (I think I've heard there are paid apps in there somewhere). It cost $1150 or so with the SSD as an extra $200 (but I have a 500gig external drive now too). It's the classic very attractive "they use these on the space station" thinkpad case, well designed with water-spill catching design et cetera.

So yes, the macbook is a good machine. But for people who aren't developing for OSX and still want well designed hardware it's hard to argue there aren't other options that are easily better if you can handle 300 grams of extra weight. And yes, I've had macbooks fail on me (case cracking and hdd failure within one year) so I think they are probably average quality in that regard (i.e. the internals don't match their good looks and are possibly compromised by them sometimes).