I was really excited to listen to this, since I read an early draft and wanted to see how it looked as a finished product!
The world-building in this one is just tremendous. Although the story didn't feel like it was part of a longer work, as it was completely self-contained, I think the world certainly could support a novel-sized story (get to work, Beth, I know you were just dying for more novel projects!) I think the ending is perfect, straddling the line between the ridiculous (everything works out for everybody and they all ride happily into the sunset) and the depressing (everybody dies, life is full of woe). Instead we get a little of both. Bittersweet.
We also get magical robot war-pegasi, which is even better.