To me too, OS X is very important. The way it works and everything else that is not objective and deals with "taste". On the objective side of things, I like the ability to be in *nix environment, run proprietary software (such as Adobe CS, a reasonable Skype, iTunes, MS Office or iWork - I definitely don't like OOo or forks, etc.) amongst other things. On the middle ground of objective and subjective, I like the fact that my OS doesn't keep slowing down with time - this can be measured but I'm not aware if someone has.