Yes, I did get a Mighty Mouse. I love it. The scroll ball feels absolutely natural, and the touch-sensitive shell works well. The only thing I need to work on is that, when mousing left-handed*, my ring finger sometimes brushes the left side of the shell just as I’m right-clicking. Since the logic seems to be “it’s a left-click unless it’s unambiguously something else”, I’ll have to fix this. As for the side buttons, I haven’t use them much so far. The default setting is to bring up Expose to switch windows, but I prefer to task-switch by using scroll-ball-click to bring up the application list, horizontally scrolling with the scroll ball, and selecting via left-click. Very easy, better than repeated cmd-tabs.
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* Even though I’m right-handed, I’ve taken to mousing left-handed about 80% of the time. Good for incipient carpal issues.