According to Martin Brinkmann over at gHacks, the latest Windows Insider build incorporates the permanent activation of asm.js in Edge, which means it'll appear in stable builds sooner rather than later.
If you're using Edge to debug asm.js, you'll be happy to know Microsoft has gone a step further: the browser's developer tools will better cooperate with optimised code:
In an effort to spice up the news, Microsoft put together an example using the Stockfish Chess engine. Two instances of the engine are pitted against one another, with one implementation asm.js optimised. Turns are limited to 200ms (though this value can be tweaked in the demo), so the faster the instance can run, the more moves it can evaluate.