It worked pretty well, although it did produce some noise with my image. However that's probably to be expected with a service like this. Nevertheless, it made the picture much more readable.
Here are the before and after photos: http://imgur.com/wPgl8&G80Lz
I agree with some of the comments. The noise around the edge of the whiteboard can be distracting. OCR would be a nice touch if you can get it to work as well.
Another thing that could be useful is automatic cropping so that the picture contains more content and less empty space. Maybe have an option to divide the picture into individual photos if there's enough whitespace? That way you could have separate photos for separate diagrams.