Nice find!
I think the biggest thing worth mentioning about HTML5 performance in general (both for Desktop and Console), is that the scope of the game is currently the performance killer. Small Atari-2600-style games (with updated graphics) will run pretty well, especially if they run fine in Canvas2D, but anything 80's arcade and newer can really start chugging, especially if it needs WebGL just to get a 30+ framerate.