Let's have a bit of sanity in this discussion.
I've been using computers, large and small, since the mid-70s (I'm 63) and they all had or have their fanboys and fangirls. The same goes for operating systems, programming languages, and everything else technical.
I've been using PCs since they arrived on the scene but have bought my first iMac (24", 2GB, 2.8GHz, 500GB), which I've had a week. I'm very pleased with it: the screen had no 'gradient issue', it hasn't frozen yet, and I'm getting used to the new keyboard. All being well, I shall move gradually to an all-Mac setup (programs and kit) because OS X is so much easier to use than Windows. XP is quite good (despite detractors, Windows 2000 wasn't bad, either) but Vista is best left alone. I'm finding OS X, in the main, more intuitive than either Windows or Linux with KDE.
There will always be jobs that Windows, Linux, or 'pure' Unix will do better than OS X and vice versa - it's 'horses for courses'. There will always be dud machines when they are mass-produced but there will also be many more that work as specified - and that applies to PCs as well as to Macs. The crucial consideration is: 'will it do what I want it to - easily, reliably, and well?'. Nothing else matters.