Have recently been converting a lot of video to .m4v format to manage video playback through Apple iTunes (7.1.1), now when I export stuff “for iPod” from my elgato eyeTV software, the resulting video files, when imported into iTunes have a description field. I have not been able to edit this field with iTunes (get info) or add descriptions to videos I have added from other sources.

Well I found a solution (although it would be nice if Apple managed to add this to a future release) over @ dougscripts, hopefully that helps someone else out there :O)