I asked Apple to loan me a new PowerBook so I could test first-hand the hardware features they added in the latest refresh a few weeks ago: the scrolling trackpad, the Sudden Motion Sensor for hard drive protection, and increased backlighting for the keyboard. You can read about these features in Apple's marketing materials, but it's nice to test them first hand.
Using the scrolling trackpad is more natural than it may sound. You use two fingers to gesture across the trackpad to simulate a mouse's scroll wheel, which works horizontally as well as vertically; the sensor has no trouble telling the difference between one finger or two. (I've been waiting since college for 3D gestural recognition; a scholar-in-resident spent a year working on that, but obviously we're not there yet.)
Apple says the keyboard backlighting is up to 10 times brighter than in the previous models, and, man, are they right. In a fully darkened room in the back of my office, I kept hitting the brighter-backlight function key and the room got brighter and brighter. It's so bright, in fact, you'll set it below maximum for most situations.
As for the Sudden Motion Sensor, which detects quick movement and locks the hard drive heads, you may ask, did I drop the PowerBook from a great height? Hey, this is a loaner, and I'm responsible for returning it intact. So, no. But I did shake it and drop it in my hands, and it surely did pause and restart the drive without a skip. For a more entertaining test of the Sudden Motion Sensor, see Amit Singh's exploration of the sensor's capabilities, including software that adapts to the PowerBook's position (such as a self-adjusting window that stabilizes itself according to how the laptop is tilted).