For Star Story, Dyrt and The Fairy Tale I did release demos showing the first parts of the game while the rest was still in development, in order to have a bit of pre-promotion indeed. Sometimes a little feedback can then also help, as some fixes or features can be easy to implement in an early stage of development, but be a downright disaster when the project is almost finished.
Now these were all games on which I had a very clear view on the entire story line and such before even starting on that. In Luna's Father I went a bit more "on the fly" and as such too much uncertain factors to go on. As soon as my revamp on Dyrt is finished, I should see to finish it though. I already implemented the final boss fight, but I was always in disagreement with myself about the game's ending.