MagicMouse is a very well designed device. I got it on the first day they were available and spent about 10 days using it. The mouse is great. Very responsive and precise. Still runs on the original batteries with about 40% charge left which means it will go for about about 3 weeks.
The gestures work great. Very usable . Especially swiping back though web pages. Scroll with momentum works and feels exactly as one in iPhone, which is very intuitive and beats Logitec's Hyper-fast scrolling feature.
There are only 2 things that bother me so far and they are really minor. First is that the thumb is positioned over 2 movable parts which creates a strange feeling that took me few days to get used to. The other thing is that if your hands are wet the fingers won't "swipe" over the mouse plastic making gestures almost impossible.
So if you live in a hot place with high humidity without air conditioning MagicMouse not may be a mouse of choice for you. In any other case - highly recommended.