It is BOTH software and hardware
People seem soooo confused about this. YES, Apple is using new hardware on the new powerbooks. Normally Synoptics makes trackpads for pretty much every laptop, including Apple. But now Apple is making the new ones in house and they run off USB instead. But a trackpad is a trackpad, there really is not much difference hardware wise for the new one. That is why the old driver that is open source and has been around since 2000 was able to be edited and perform right. The only problem, and it is negligable, is that the new USB trackpads Apple uses run more smoothly for the scrolling. I installed this hack on my powerbook and use rotational scrolling, like an ipod, and it works great. It only does not perform well when I move my fingers slowly, and it jerks. The new trackpads fix that. So yes Virginia, there is new hardware, but that doesn't matter.