This is probably outside your vision for the product, but adding a text box tool would transform this into a pretty amazing notebook app. All the type-and-draw

This is probably outside your vision for the product, but adding a text box tool would transform this into a pretty amazing notebook app. All the type-and-draw apps I've used are locked into the physical concept of a page, and combining a ZUI with art tools and text would be a delightfully organic way to take notes, build loose wireframes, or annotate concept sketches.