That depends on you. From the article:

    Alternatively, many ES.next features can be experimented with using Google's
    Traceur transpiler (useful unit tests with examples here) and there are shims
    available for other features via projects such as ES6-Shim and Harmony
    Collections.'

There's also another quite comprehensive ES6 transpiler named six: https://github.com/matthewrobb/six

no it depends on browser vendors. Transpilers dont make generators or proxies magically works in ES5.

I doubt we will ever get to use them, unless Windows 8 turns out to be such a clusterfuck that it takes Microsoft down with it.

IE9 still can't draw stroked text, for example.

Same thing here, specially having to support IE all the time. :(

Same thing here :(

The compatibility table is here: http://kangax.github.com/es5-compat-table/es6/

Result: IE10 supports exactly zero of these features. We can start using them (maybe) once IE10 is dead.

Shhhhh Microsoft doesn't read the web.... they were completely unaware that ES6 was coming. The same way they were with HTML5 and much of CSS3. If only their employees were allowed to surf the net and see what cool stuff is being invented. Oh well, off to work on my cool ActiveX/VML Flash Shim....

Microsoft has a representative on TC39 (Luke Hoban) who is extremely active. In fact, I usually find that my thoughts on some new feature closely align with his.

Because Microsoft has bet on JavaScript heavily for Windows 8 apps (at least for now), and Windows 8 apps have full support for ES5, they have very good insights about ES5.

ES6 is still "coming". Many features are still in flux, and I don't blame Microsoft for not committing to in-flux ES6 features in the timeline of IE10.