Pros

• Beautifully rendered documentation.
• Supports different themes.
• Flexible document stucture representation which uses CommonDoc.
• You can write your own markup engines in for CommonDoc and they should work with Codex.

• You can choose in which markup docstrings are.

  Right now CommonDoc supports only two formats: Scriba and VerTeX

• CommonDoc and Scriba has extensions to render plots and TeX formulas. And it is relatively easy to write new extensions.
• There is a special tag to reference a symbols from CL specification.

Cons

• Default markup language is Scriba. And you have to learn it.
• Scriba is powerful, but hard to read because of heavy usage of markup keywords.
• Errors in markup is hard to debug because you have to inspect backtraces.
• There is no cross-referencing feature.
• I didn't find how to make Codex to generate index.html file