The App Store is a fiercely competitive place. Mindsketch has not managed to gain traction. It's a shame, I think it is very powerful but I have not found out how to communicate what it can be used for.
It has a small feature set. I would say it's focused, trying to make one thing well: allowing huge drawings that assist your mind. However, I've learned that many users find it limiting. For example, though huge, the canvas is not infinite.
Today I've decided to make Mindsketch free. I've started working on a successor and plan to keep Mindsketch available until the successor hits the market.
Unfortunately, it's not available in the EU for now.