let, generators, list comprehensions, patterns, E4X, etc. but may eventually support ones that are/become Harmony proposals. I'll probably add patterns next because those are pretty sweet.
Builders are also supported.
Parsing large files can be slow, for reasons articulated by Andy Chu.
You can download a standalone version of reflect.js to embed in web pages here.
Reflect.js is available as a CommonJS module for Node.js. Simply install it with npm:
npm install reflect
MIT X Licensed.