I don't actually do enough coding to say for sure, but this looks potentially hella-awesome. http://vimeo.com/7405114
Cool, I'd seen a demo about it a while ago, or of a similiar approach. For me personally I doubt it's worth it to add an abstraction layer like that in my head while writing html, but I presume when you get used to it it will speed things up.
I get by pretty good with copy/paste/replace variations and prefer the hands-on way, but then again I don't write a lot of plain html - most of our html content is created by xslt transformations. If you do a lot of html layout on a day to day basis I'm positive it can be a great asset.
I suppose its similar to putting jquery on top of javascript. it takes care of the crap cross browser mayhem and let's you code.
The web is evolving in a great direction lately. I like it.