The good news is that, of all the book promotion widgets I've seen, MyBooks is by far the best. Combined with their Reviews widget, they are a step away from greatness. But there are a still a few things missing.
1) Booksellers - It's great that they offer support for Amazon, Barnes and Noble, iBooks, Audible, and a few other independent sellers. But there are still some crucial ones that are missing, such as Smashwords. As a Smashwords author myself, the lack of a Smashwords link support is a big detriment.
2) Short-code - Having a short-code to implement in the page is great, but the problem is this will bring up every book. I have a few different book series as well as books that aren't in any series. Ideally, I would love to categorize my books based on series, so I would have a link for The Myth Hunter Books, Infernum Books, and Other Books, and then on each page, I would display only the books for that category.
If Out:think could implement these two simple yet extremely valuable features, we're looking at an extremely powerful self-promotion tool.