So I was playing with Apple's new mouse a couple days ago (yes, they licensed the name). It feels exactly the same as Apple's previous mouse, with the addition of the tiny scroll ball, but it can right-click.
Users who actually like Apple's one-button mouse will still like this just as much. It can be configured to behave as a one-button mouse, and it doesn't have separate left and right buttons like other mice do; you can click in the middle with both fingers and it feels exactly the same as a one-button mouse. However, those of us who are used to right-clicking won't have an easy time of it. To get a right-click to consistently register as a right-click, you have to actually lift your left finger off of the mouse while right-clicking. Otherwise it will detect it as a left-click about half the time, depending on where you click and how you're holding it.
The scroll ball does very well at figuring out whether I want to scroll vertically or horizontally, which is good (you probably almost never actually want to do both at once). Unfortunately, the ball's small size means you have to move your finger a lot more than on other mice with large wheels, which is annoying.
I had no trouble middle-clicking - you sort of click while pressing the scroll ball, which sounds weird but feels less awkward than clicking the scroll wheel on most other mice. Squeezing the sides gives you a fourth click, which also works quite well. Other than having to lift my index finger to do a right-click, and having to wiggle my finger a lot to scroll, it's a good mouse, but those two issues would drive me crazy, and I can get a good mouse for less than half the price, so I don't think I'll be buying one.