Really nice tutorials, the background music is nice too, the pace is pretty fast as well which is something you don't usually see on tutorials, however this is way better than a slow presentation which makes it unbearable to watch after a point. Never used d3.js before, however i really enjoyed the tutorials. I ended up watching 3-4 of them and got interested on the library.

The only negative comment i guess i can make (as a suggestion) is that on some videos the music is a bit high which ends up overlapping with your voice.