Does this leave enough meta data for other book readers? You can listen to them in a generic audio player but I like having something that understand the chapter breaks.

You have to copy the video as well if you want to keep all the metadata, chapters, and cover art. I'd suggest converting to m4b rather than mp4. I gave an example in my other comment in this thread.

Does this really work?

Yes, it does. You'll have to use the correct activation bytes to decrypt, but those can be retrieved by signing into the audible account.

How do I read those out when logged in?