I appreciate the work that must have gone into this, and it looks like it has been done well technically. However: How many people are this deep in the world of Ruby and yet also enjoy writing WordPress themes? I run a forum devoted to WordPress, and I can not imagine any of the experts (who post there) wanting to switch over to Haml or Coffeescript. Most people who use WordPress are either designers or programmers who are looking to put up a somewhat quick-n-dirty CMS.
If you have the skills and resources to install a Ruby environment and a bunch of gems, why not use Rails plus some CMS built with Rails?