Took me a while to realize this also applies to the magic trackpad and integrated trackpad on macbooks, but it is nice to be able to customize it. The trackpads even have two clicks the second being a "deep" click which requires even more pressure than a regular click.
It's pretty easy to notice with the magic trackpad—it loses its ability to be "clicked" when it loses power/when you turn it off.
(The trackpad on the laptop does as well, but I feel like you're just less likely to try clicking the trackpad on a macbook/MBP if the computer's not on. Whereas with the external one, you'll notice it when you go to pick it up/move it around and it doesn't accidentally click in your hand.)
Also a nice feature, which unfortunately not a lot of applications use, is the haptic feedback. E.g. when you drag an object in OmniGraffle, you will feel very subtle feedback in the trackpad when two objects align.
Almost 20 years ago I had a cool Logitech mouse that did this. The mouse had a haptic (Synaptics, I think?) engine in it, and when you moved the cursor over buttons, menus, or other UI elements, it would give a slight “tick” as you crossed each boundary. It was very cool. There was a lot of customization available for it as well.
I had to ditch that mouse when I switched to Linux. I think it didn’t have any standard HID-type driver or something.
