Yes, the MagicMouse looks pretty cool, I may have to try it when I get my next Mac. So far, my 24” iMac is working nicely enough. =:-D
I was happy with my 20" iMac, but dissatisfied with the scroll ball, which I could never clean satisfactorily; it would work briefly and then fail. The touch surface on the Magic Mouse provides the functionality that the original mouse was designed to have, but wasn't reliable at. If you like scrolling, you might want the new mouse even if your Mac is otherwise fine.
I have a MagicMouse. I’ve had it for less than a week and so far I really like it.
I had gone through 3 Mighty mouse, they were nothing but junk within a month or two. The scrolling balls quit on each of them. Apple was great in quickly replacing them, but I finally told them to give me something else... the next day my MagicMouse arrived at no charge. No more dirty balls.
The MagicMouse is small and it would fit me better if there was more to it, but I’m getting use to it’s size.