My opinion will be based on workflow.
OsX vs Win: I like window's workflow...the classic XP workflow to be more precise. You can do everything without touching the mouse, the shortcuts are simple and intuitive, when you click something it happens right away, not after some cheap animation or rainbow circle. It feels like the computer says "ay ay sir" and obeys as quickly as it can...while with a Mac, even when you turn off everything, there's a slight delay in action that make it confusing..."did I press it? did it understand? should I press it again?". I don't have time to second guess myself and I hate eye candy when working with a computer. I want everything to happen right away, If I need to launch a program, I don't want to stare at the desktop and double-click an icon...my mouse is too far away, I press Win+R for run and type my program's name in it so I can access everything I want (win7 is even simpler)....this is for theses applications I could not fit on my custom shortcuts.. (ex: ctrl+shift+alt+c = calculator)...as for the interface in general....I hate the fact that you can't maximize windows completely...it does not give you control like pressing "alt+space" in windows ...alt+space+n or alt+space+x will either minimize or maximize my window...in OsX, you have to drag the corner until it's more or less full screen...It's not useful and when speed is important, I can't trust a Mac even though I've used them for more than 10 years!
ps: there too many different possibilities with Linux for me to talk about it here, but some distribution rocks! It's just too bad I don't really need them!
oh and I don't hate Apple, just the way they make everything so simple that once you are good at it, you can't really step it up! Apple makes nice machines for simple users. I like the experience, but in my mind a work computer will always be a PC-win or linux!