It's rubbish. The Multi-touch features are so beautiful but overall the mouse is the most uncomfortable mouse I've ever used. It's a very poor shape and the "click down" to click is rubbish.
I wish Logitech would come out with a decent cordless with multi-touch features... Logitech mice are the bomb. I use a G9X on my iMac and with acceleration disabled to correct Apple's horrid acceleration curves it rocks.
do you mean you bought a mighty mouse and it sucked, and are now wondering about a magic mouse? or is there a new mouse I don't know about?
As far as the magic mouse is concerned, I'm in the minority that likes it. The shape of the mouse was very uncomfortable at first, but eventually I found a good way to hold it that feels good. The multi-touch is amazing in osx, but only with BetterTouchTools (which is free). BTT allows you to map a crazy amount of gestures to all sorts of different commands. Having expose and spaces execute off the mouse is awesome. The scrolling is really nice too. You can flick to scroll very fast or keep your finger on it to scroll with precision.
I know most people like the idea, but hate the shape. You probably won't find a whole lot of love for it around here. Overall, I like it a lot. That being said, mine was a gift and I don't do any gaming on my macbook, so I am a little less critical of it. It is very expensive and it would be absolute shit for gaming.
Basically, I hold it with my thumb and pinky, and my other three fingers hover over the top. The uncomfortable part (and many will say this is the fatal flaw of any multi-touch mouse) is you can't rest your fingers on the top of the mouse. This is very unnatural at first, and took time to get used to.