Awesome game! I really appreciate the art and the smooth gameplay. I think Down Hole could do with more powerful powerups. I found myself not being able to utilize them a lot (except the hearts and coins).
The game can feel like a maze at times, but this is a good thing. It allows for a slower moment in a faster game. The fast parts could be faster, though. There isn't much utilization of terminal velocity in the game, which would be really cool to see.
Finally, I think the direction of the game is really cool. It is unique and has lots of potential. The art is fantastic, but that is a given for this developer's games. The sound effects are very nice and work well with the physics and art style. All in all, this is a great game that is definitely worth a play.