I did not read the article in-depth but class D audio amplifiers use variable pulse widths and then filter it before the speaker. Aside from very good efficiency you also remove the need for a transformer using this method hence why its used.
I'm not sure which is the hard part you're referring to- implementing the amplifier itself, or the board around it. I don't think an amateur would want to build their own class-D from raw components except for pedagogical purposes.
(i've been pretty happy with the results, I used the board to drive a couple speakers and the amplifier is not the first thing I'd fix to improve the audio quality.