What software companies have forgotten is that the job of the OS is to GET OUT OF THE WAY. It's your content that matters... and the OS is there to help you access and manipulate that content as naturally as possible. That's it. The desktop is an outdated idea, and there's been progress to move beyond it in various places like MIT, but nothing has really caught on (and Microsoft's business tactics are probably partly responsible there).
Anyone see Minority Report? They consulted people who develop this kind of thing when they made the movie. Remember the computer interface? The OS was invisible... you had only your content and a way to utilize it. I don't know how viable the gloves were as an input device (kinda like learning sign language to use your computer)... but that was a pretty good example of where we could be going if we'd stop thinking in icons (abstractions). As we gain more and more processing power, we require less and less abstraction to "compress" the way our content is represented.
I agree that Apple puts faaar more study into usability than Microsoft (in fact there's a very short list of things Microsoft has actually developed rather than bought or hijacked)... but they all need to be reminded that they belong behind the scenes, in my opinion. It seems like the Unix/Linux world is ahead as far as that's concerned, but I haven't used them enough to know, really.
EDIT: Err, sorry, I guess I've just contributed to the hijacking...