This will be great for things like node-webkit or atom-shell (and node in general). There are many use cases where using an optimized subset is a big win, like

This will be great for things like node-webkit or atom-shell (and node in general). There are many use cases where using an optimized subset is a big win, like atom.io or any cross-platform app with an embedded V8. Granted, it won't speed up DOM operations much, but JS is being used in so many non-browser places... it's good to know that the language performance isn't stuck against a wall.