Everything that you mentioned, and also: the relentless miniaturization. That took a lot of engineering.
It's emphasized in the video linked to in the OP, but it disappears in the images linked in the response above, which are not proportional. Here's a side-by-side comparison:
All these years later, and with the new MBP, they're still pushing system miniaturization, flash memory, and high-res color displays. It's a straight line in some respects.
