If you purchased a Magic trackpad today, you’ll need to do a good old fashioned Software Update to get the software working on it properly. You’ll also need 10.6.4 to get inertial scrolling and the three-finger drag gesturing working properly as well. More info including manual update here.
Oh, and if you have a MacBook/Pro, you get inertial scrolling and the three-finger drag gesturing as well.
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