There's one major issue I have with this plug-in: the cursor off-set on main tool.
Using this with an active digitizer pen / touchscreen makes the whole thing unusable.

For me the main drawing tool (pencil) draws about 20 pixels below where I draw with the actual digitizer pen or have my actual browser's cursor (can be seen via "Show location of pointed when I press CTRL key").
Strangely enough, line tools work perfectly and have no offset. For mouse users this is probably not a noticeable issue, but for digital pen users this pretty much ruins the whole thing.

Also sampling tool doesn't work correctly and eraser tool is offset as well.

Regardless I'm giving this app 4/5 because this is not an issue for many users and because it's just a bit short from being the #1 notes app for digitizers. Hopefully developers will fix offset issues. I'll change to five stars if main tool's cursor offset is fixed.