It's a rich text editor from developer James Hoover that is surprisingly powerful, very lean, and open source. It's the perfect in-between text editor, nestled somewhere east of Microsoft Word and west of TextEdit. It's small, fast, and easy to use.
Features of Bean (the app, not the Mr.) include live word count, in-depth statistics, autosaves and dated backups, page layout mode, dictionary, word completion, and in-line graphics. If you feel a need to add some functionality to Bean, the Objective-C source code is readily available.
Bean reads and writes .rtf, .rtfd, .txt, .html, and .webarchive formats, and can transparently import and export to and from .doc, .docx, .odt, and .xml formats. It can also export to .html, .pdf, .doc, and .rtf formats (the latter two with images intact).
All I can say is that I can see why Giles likes Bean. It rocks!