• Apple killed the third mouse button! I am conditioned to open tabs in browsers with the a middle click, so this is quite some problem for me. (I still hoped for an Open-in-a-New-Tab gesture for Apple’s touch pads but I guess it is unlikely now.)
• You have to press down the entire mouse to generate a click. Not really new but on this mouse I instinctively try to use Tap-to-Click like on a touch pad. It just does not work that way. Bummer.
• Right click still requires you to lift your left finger like with the Mighty Mouse. This requires some time to get used to and also means that it is impossible to press both “buttons” at the same time.
• Scrolling with one finger works fine but touch pad conditioning kicks in again here: I tend to try scrolling with two fingers.
• There are no gestures for Exposé and Spaces. Would have been nice.

And it is flat. Almost too flat for my hands.
My conclusion is that Apple can always come up with interesting mouse concepts but still fails at actually building usable mice.