Eh, the problem with JS is that it's starting to suffer the language feature bloat that, say, C++ has. I think the party will end in like 5 years, mostly after introduction of shared memory objects and traits.

Meanwhile, this is going to allow people to port really dumb things into the browser and expose all sorts of new crazy.

Still neat, I agree, if you prefer native code. That said, it's not an unalloyed good.