My observation on their demo, with 64-bit Firefox Nightly for Windows on a Surface Book (i7-6600U, using integrated graphics):

• For most of the filters, WebAssembly averages 10–40% slower than JavaScript;

• For some of the filters, WebAssembly averages −10%–40% faster than JavaScript;

• For Super Edge, WebAssembly averages 10–20× faster than JavaScript;

• Beards look even cooler than normal with Super Edge (though I wouldn’t want my beard to look like that in real life).

What I always found interesting is the (psychological) asymmetry

+50% means 50% slower

-50% means twice as fast

(or with stocks, going down 50% means you lose half of your money, going back to the original value means you double your investment (for new investors) which I think basically drives stock market investments)

Also, one reason I am excited about WebAssembly is because it is a low-level target for compiled languages that is also cross-platform. I know others exist, too, but I think this being the web will cause more and more people to get into writing compiled languages :)

And SIMD: https://github.com/WebAssembly/design/issues/1075