It's been a year since I bought an Apple MacBook to replace my older Apple iBook. It has a trackpad that you can move a finger around to control a mouse, but I found out by accident this morning that by dragging two fingers on it, you can scroll.
It's amazing. You can scroll quickly with a flick of your fingers (or a flick of one finger while another rests elsewhere on the pad), or slowly move the page around as if you were shoving a paper around on a desk. The up/down scroll is really useful for web pages, but all four directions are nice when looking at a large image on the small laptop screen.
Clearly, this OSX feature is the forerunner of the ultra-cool interface seen in the iPhone adds (or in person, if you have one — something not an option yet for me in Kyoto).
I'm not sure what's more amazing, this feature or that I've had the laptop for a year before noticing it. I've known about it for only a few hours now, but its use is already second nature.
A related feature I discovered about a month ago is that if you move two fingers up on the trackpad while holding down the control key, it zooms the entire screen. Sometimes I would do this by accident while using the control key while typing quickly, somehow bumping the trackpad with my thumbs enough for the zoom feature to click in, but only a little. It would quickly auto-snap back to normal, so the effect to an unknowing me was exactly that which I'd expect to see with an LCD starting to fritz out. I was this close to calling Apple Support when I finally noticed what was going on, and realized you could use the feature to zoom way up (20×).
Sweet.