Looks great, game changing in fact. It seems to be quite inline with Brent Victor's vision (http://vimeo.com/36579366). One thing I'd like to see stolen from his demo: Once you have direct visual feedback on what you're doing, it makes a lot of sense to have widgets for your style definitions, e.g. scales with handlebars and color pickers popping up when the cursor is over values with corresponding type. It's a great thing that this project is both funded and open source. Quite unexpected from Adobe tbh.