This article neatly sums up my thoughts on asm.js. On the one hand, I really like the fact that Mozilla is doing a lot to promote Javascript (which I usually enjoy programming in). On the other, asm.js basically destroys any reason to write Javascript.
For someone interested in web-based gaming, it really discourages me from investing in Javascript-based tools, since the future _won't_ be hand-written Javascript. It's only a matter of time before a tool like Unity includes an asm.js export target.
We spend too much time developing languages instead of environments. Unity is a good environment for developing games. If your goal is to make a game you should use Unity (or whatever... GameMaker has an HTML5 export module; use that). Javascript has nothing to offer you to enhance your productivity and develop your game.
I disagree, I think the future will be all kinds of things, both on the web and elsewhere. On the web, it will be both handwritten JS as well as compiled JS from various languages like C/C++ (into asm.js), TypeScript, etc.
Each of those is good for some use cases, but none is good enough for everything. Just like we have many languages for native development and web servers and so forth.
For someone interested in web-based gaming, it really discourages me from investing in Javascript-based tools, since the future _won't_ be hand-written Javascript. It's only a matter of time before a tool like Unity includes an asm.js export target.