Then I started using Mac OS X and I realized that it's actually nice to be able to select text and NOT have it auto-copied obliterating my clipboard, but instead be able to replace it using Command-V. And it's a pretty cool invention that the same shortcuts work in all applications, consistently. And that I can copy text in any application and paste it in any other using the same shortcut. And that I don't have to use the middle mouse button, which is a scrollwheel these days and is difficult to hit without invoking the scroll functionality. And it's pretty nice to be able to paste to where the cursor is RIGHT NOW without carefully positioning the mouse pointer and making sure it doesn't move while you carefully try to hit the middle button (otherwise your text will get inserted wherever the mouse moves in the meantime, if you are in a browser edit window).
I could go on. There are so many things which can be done better if we drop the "the way X11 did this is the best way, ever" attitude.
And then, eventually, once we get text copy/paste right, we can get to copying images, which again is a totally solved problem on Mac OS X.