I feel that feature wise the game is basically complete. From here it is about refining the ideas and evaluating them for improvements / changes.
To read up on the progress of the game so far, you can check out the previous developer diaries here.
Most recently I have been trying to update the presentation of the game to make it look more appealing. Right now I am playing around with the challenge award graphics to make them look more interesting. Compare these to the other ones in the gallery and see what you think.