One big thing that's missing is a meta description tag. This doesn't affect ranking so much any more, but it's often used in results listings and sometimes relevancy. It's also a good place to put all the buzzwords we might not want to stuff into a slogan.
Here's a first run:
The open source content management framework for building everything from personal blogs to complex web applications. Much more than a CMS.
That runs to 160 characters. Needs to be between 150-250 - hard to fit CMS into the first sentence.