3 things that would make the App perfect.
I've used SNotes for a while on my tablet, and although it has some really nice features, somehow the way it feels annoys me tremendously.
Papyrus is simple and beaitiful and I love that you can use ultra thin writing as well as setting your page size (S Notes is fixed to A5).
The pressure setting is slightly bugged and makes the screen black out for a while at times, but doesnt crash the tablet. I turn it off in lectures.
Now for the ideas. Adding a dropdown menu to the left and right of the screen and letting the user choose which to use will allow for faster change between pen settings on the fly.
Although the palm detection is very good, using two fingers for both pan and zoom means I often change the zoom settings when I pan. I suggest a zoomlock which fixes the zoom to whatever the user prefers, but that can still be turned on and off on the fly. Many users ask for a fix to screen width setting, but I believe this could solve that too as well as give users who like zoomed notes more stability.
The only other main feature I would love to see is the ability to import pdfs to make annotations on as well as the ability to add additional note pages in between. A highlighter with variable transparency would complement this feature well.