What impresses me the most is the JS. It is so clean, concise, and, the only other word that I can think of, professional. It puts the onus of capability on the browser and doesn't try to make up for those who lack. Sure you can shim addEventListener or setAttribut, but F IE (really), it has been adding complexity for far too long.
Thanks for pointing this out. Based on your comment I reviewed and the style is really nice. I haven't seen that method of returning the public API before but like you said, it is very clean.
