What I love about Documents is the immediate paddings and margins they apply in each style. Paper seems to have them on 0.
What I mean is this. When you apply a Header 1 in paper it gives you immediate margins. Also in H2. But that's it. All other formats get a zero margin.
I don't need much. Just half a line even less. I know it's not something big, but your formatting between elements is so agly. Please when I press enter to change a paragraph give me more that 0 margin. Also between paragraphs and Bulleted List, Check Boxes, and more.
You get the ides. It isn't something you need a lot of time to do. Just A/B Test it in 1000 users and see reactions.