Googlecast (the software side of Chromecast's magic) is the real winner here. Having a device that can stream ANY content in a couple simple API calls is unlike anything on the market currently.
Chromecast supports everything chrome does (audio, video, web sockets, canvas, web audio, etc.) and it all just works unlike most of the TV dongles on the market today (which usually have issues with google play, Netflix, and/or Hulu).
As I said, I agree with your comment that the software is the good part (or magic as you call it).
The magic word comment was about the TC writer expression about the hardware of the device, which is not that magic in my opinion.
Chromecast supports everything chrome does (audio, video, web sockets, canvas, web audio, etc.) and it all just works unlike most of the TV dongles on the market today (which usually have issues with google play, Netflix, and/or Hulu).