I don't think it's the design, it's the usability. I might argue that it has always more about usability than design.

Sure, the iconic designs of the G4 Cube, iMac, metal Powerbooks and later Macbook were what drew people in, but the usability is what kept many people with Apple.

Is the better scrolling a design or a tech thing? Probably tech, but I'm sure it's only that good because someone really understood how people use it and what it really needs to do well and then insisted that the tech worked flawlessly.