I've updated the plugin (v0.6.74) to parse metadata from the following file formats:
.MP3 - original format, but more robust parsing.
.M4B, .M4A - second file format, more complete parsing.
.AA, .AAX - the new file format.
.MP4, .FLV, .3GP, 3G2. QT - happen to have the same file format as .M4B, so why not.
No attempt is made to bypass DRM. Only public metadata is parsed from the files for the purpose of managing the books/files in Calibre.
I have not tested it with .FLV, .3GP, 3G2. QT only because I don't have any examples. I have tested it with Audio Books in the .aa and .mp4 formats.
CAVEAT: You still have to switch the Add Books file type to "All Books", or drag-and-drop the files onto Calibre.
I have not yet tackled the GUI tweaks in Calibre.