Only features specific to the product is documented, i.e. you have to go outside the TextMate documentation to learn about regular expressions or shell commands, even though they play a central part in TextMate. Also, features are generally documented only in the form of “it is there, here is how to enable it” and possibly which options you can tweak. If you seek examples of how to use the feature in a workflow, you will again have to seek outside the documentation.

I do try to augment this reference style documentation with screencasts and blog posts about specific topics, but in general this is the style I am content with, because my core competence is not writing tutorial style documentation nor is it to promote knowledge which is not specific to TextMate (even when usable in TextMate).

Your comment is unclear as to whether you feel the current documentation requires improving, or if you had hoped I would branch into the latter style of documentation, now covered by a third party book.

Ideally I should hire writers like James and include their writings with TextMate, but if I do that, you should be prepared to pay a little more than €39 for the product ;)