The main limiting factor in using this gem (came across it with nanoc) was that the W3C still doesn't use CSS3 as a default profile, even though it's been in common use for years now.
Other cleanups were made as well, such as using bundler.
Step One: Use Bundler and update to new RDoc command
Step Two: Mark broken tests as pending
Step Three: Use CSS3 as default profile
Awesome, thank you.