First off, this is cool. It is tremendously exciting to see the bar for hardware hacking getting lower and lower. To the people complaining "Why JS? C is fine!", remember that once the complaint was "Why C? ASM is fine!".
At the same time, I can't help but grin that we on the CS side find a way to erase all the gains in performance and efficiency as soon as the EE guys make them.
There has to be come kind of universal constant: the limit, as technology proceeds into the future, of the execution time of "Hello World" is some fixed number. Because as soon as we get better hardware, we invent an even weightier runtime environment to slap on it. ;)