It would be nice if instead of using touch to draw, a swiping touch gesture would be used to move between pages.
Also, if you could navigate through pages as if they were a notebook, with one page on top of another.
Since I am a developer myself, I know this might be hard: if swiping on the page could "peel back" the paper to reveal or cover the page underneath.
I drew this idea in Xournal and attached it below.
Frankly, I find pushing the next/previous page buttons a bit hard.
A Delete Page button would also come in handy.
Sometimes, I find myself squeezing in text at the bottom of a page. I was thinking about an "Infinite sheet of paper" option that allowed note writing to continue on and on without boundaries, either just downwards or in all directions.