Although much of the recent scrolling hoopla is with Apple's new scrolling Mighty Mouse, I'm here to extoll the virtues two finger scrolling available with Apple's trackpads on their laptops.
Originally introduced with the last PowerBooks, Apple's two finger scrolling is now standard across all its laptops, so the last iBooks got it too. I have just purchased a 12" iBook and have come to love Apple's implementation of trackpad scrolling.
I have never liked the limited up/down scrolling on scroll mice, and didn't like the trackpad scrolling hacks with 3rd party apps either. Thus, I thought I wouldn't like trackpad scrolling, but it's a world of difference. Not only is it very smooth, but it also works in all directions. This is especially useful for large photographs, say for example in Preview or Safari. With two finger scrolling, I can scroll up, down, right, left, sideways, or even in circles. Diagonal and circular scrolling do not work quite as smoothly in Photoshop CS, but I'm sure it will improve with subsequent updates to Photoshop and/or the scrolling driver. (I have not yet tried Photoshop CS2 however.)
It's these little features that continue to make Apple's laptops so desirable.