Still some work to do, but here's proof: What makes it even better is this is less than an hour or so of work. About 30 minutes a couple of months ago to get the patch started, then I sat down tonight to see how much was left to do (expecting lots of slogging it out), and within another 30 minutes there's the field fully functional. That's in the region of 20-odd lines of code to make your entity fieldable in Drupal 7. Unbelievable simple.