The CSS Playground is a preview of our CSS styling tools, and we'll be adding some of our other components (layout, adding new elements, code export) soon. Currently, it only works in Chrome, but we're working hard to add Firefox support.
Edit: After studying the video: I'll pay triple! Any thoughts on importing bootstrap?
We're actually big fans of the MailChimp pricing model (both pay-as-you go and monthly options), so it's a possibility.
About Bootstrap, the current demo already uses it for the non-visual elements (grid, etc), but we're still not sure about a whole-scale import yet. There are a lot of changes afoot with Bootstrap and Foundation (mobile-first being a big trend), so we're noodling on a ton of options.
I worked with Brackets team. I know which direction they are going and this is so inline with that.
Good luck.
Anyway, I'm signing for updates because I know people that would be interested on your current offering.
If you don't mind me asking, what were your backgrounds before you starting working on this?
I've been doing freelance web design on the side for a long time (actually bought the webflow.com domain in college for that purpose, going into a lot of debt in the process), then worked at Intuit for several years on an a social enterprise product. Studied CS at CalPoly, and spent a few years wandering through art school in SF before that.
My brother (Sergie) studied at UCSD and worked as a creative director for MuirSkate.com prior to starting work on Webflow. You can see his (now outdated) portfolio here: http://sergie.info/
Freakin gorgeous!