Firstly, thank you for all the feedback most of which has been positive. I know the graphics are simple and people like to look at "nice" things but I write code for a living. My graphical ability ends with drawing stick figures, I'm sure a 3yr old with a crayon could do a better job.
Don't forget you can use the "Send email to developer" link to provide feedback. I have read everything sent thus far and will be releasing an update next week.
I apologize to the people who found the crash bug on level 2. This was the first item I fixed, nice find!