Amazing post, Dave, and definitely an important topic. My first book I used one of the larger “editorial agencies” you mentioned. The quality wasn’t bad but there was no direct contact with the editor. Just ship it to them and they ship it back. I’ve tried out several editors now and found a very good one who did a great job on my list book. Once you find a good editor, stick with him/her and build a relationship if you can. Thanks for the list provided and this editors test is a great addition.
It’s always sensible to follow due diligence in submitting your first draft of your book to an editor by making as fool-proof a copy as possible for you because first, it is your own creation, and secondly, a horrid draft sent your editor can end up frustrating both you and him or her. Make your own corrections to the extent you can, so that will make the job of your editor that much lighter and the end result would be a lot more effective.