When you scroll on Goodnotes, the paper seems to take too long to stop moving after swiping and you must wait until it stops before you can swipe again. Getting rid of some of this extra moving time would make the app feel a lot more fluid.

There is also quite a bit more Apple Pencil latency when using it in Goodnotes vs a native app such as Apple notes. Not sure why this is but working on this aspect would boost the entire feel of the app and make it feel more integrated and polished.