When you're talking about ease of use though mostly you're talking about learning curve. Something with a steep learning curve which is easy once you figure it out is what we generally call "expert friendly". Expert friendly isn't entirely a bad thing, it's good to have strong features for power users, but if you want to bust into the mass market you need a shallow learning curve that eventually leads to power user capabilities for those that want to dig that deep. To rule the desktop world you need to get as close to possible to appliance level of initial usability, pretty much anybody that's ever heard of a microwave or toaster or Foreman grill can take one out of the box and cook something with it in the first 10 minutes. Really Mac has consistently come the closest to that, depending on who you're buying from pre-configured WindowsXP comes in anywhere from a close to distant 2nd, Linux and company are sitting near the bottom slightly easier than Win3.1 (which had some horribly counterintuitive things about it). But they're improving the Linux variants, the hard part is keeping the power users happy while dumbing down the first 10 minutes, seems like they're on the right path though.
I'm not trying to start a flame war here--it's an honest question--but why do you rank Linux below Windows? Why is Apple above them? I've never used a Mac, so I don't kow anything about them.