Speaking of this site, I think it and others like it are interesting, but let's face it, as a usability person myself, we can debate minutia, data and theory until the sun goes down. However, as someone who has used both PCs and Macs for years and years there is something unquantifiable going on. I simply feel better and enjoy my Macs more - a lot more - especially since OS X! If we try to pick apart why I love my Mac and/or don't love my Windows machines, well, I'm just not sure it would work (or be much fun).
Donald Norman, another usability "guru" who many people can love or hate has taken up on this idea in his exploration of "emotional design" - why we love or hate the things we use. Donald approaches this as a revelation, but for industrial, graphic and product designers outside of computers, this is very old news. I imagine designers would laugh at the attempts to quantify this sort of thing. You can't create a formula for it, you either have designers who "get it" or don't. Apple may make some usability errors here and there, but overall they certainly "get it."