And when prompted, Apple may look here to get more info / examples -- while I was on the phone to support, for example, I told the operator the title of this thread and she had a quick look.
Anyway, the main point of writing -- Data Rescue 3 has finished, after 70 hours. It was reporting 3 million files while scanning but after analysis it's down to a more sensible number of thousands. Most of them look like they're there.
It has not fully restored any structure, but I can see why previous posters might have thought it had, at first: the files are arranged into a practical structure, by file type, including "Audio", "Movies", etc. and where possible very sensible filenames have been attached. For example, it's drilled down into fonts to find their names, and into some audio files to get the track title from the ID3 tags or wherever. With images it's gone for a date from the EXIF, or failing that, for the size in pixels. Pretty useful. My iMovie and Final Cut projects are pretty jumbled up though, so that's where manual work will be required. Be sure to look in "orphans" if you get that; in there I randomly found Adobe Font Folio!