Progress is coming along nicely. All levels except one are completely finished. About half the sound effects are in. The story is mostly complete, in that most of the material has been covered, but the parts that I still have to write are going to involve the most writing. So time-wise, the story is about half done. Originally I planned on having a stamina system tied to drinking water, but I ended up removing it in favor of a more traditional "running uses stamina, walking or standing still regains it" approach. Then I took out running altogether. So... yeah :P.
Originally I expected The Moon Sliver to take roughly 20 minutes to complete. That was before I decided to sell it. Now, it's probably closer to an hour. However, the free-form nature of the game means that players could easily take more or less time, depending on how thoroughly they explore the island.