We went through the entire app, and examined each piece of text. For those pieces of text that were too small, we increased the size to match the smallest text found in Apple's own apps. For each piece of text that was too large (mainly the task title), we decreased the font size to allow more information to fit on screen. We then tested this with several people outside of Toodledo, including people of different ages and eyesight ability to make sure that all our fonts were readable.
Jake, I appreciate the testing, but the folder fonts are too small. Optimally, you should give customers the choice of font sizes to use. I have boosted the default fonts on the iPhone, but Toodledo doesn't recognize it. The fonts on the tasks themselves are fine.