It's All Text Firefox Extension

Has anyone tried the It's All Text Firefox add-on?

It allows you to edit the content of HTML textareas with your favorite text editor.

The Firefox extension creates a small "edit" button at the bottom right corner of every text box like this:

If you click on the edit button it opens your favorite text editor (I use gvim). When you save the document in your text editor, it sends the text into the Web page's textarea.

Download it here.