Markers are now more explicitly named and related to how the line will respond. For example, the mechanical pencil is fixed width and grainy (does not seem to respond to pressure as much as one might expect).
Fixed most of the areas I would have had recommendations for regarding Codex 1.0+.
Screen stays awake for long periods of time.
Swipe gestures can cause you to turn the page when you're not expecting. Like if you point and something and slide your finger horizontally across the screen.
Thoughts and Recommendations
Be able to position the tool drawer; or, change the rational default to be the "top" for portrait or landscape orientations.
Show currently selected line instead of generic icon.
At least four colors. Five might make more sense: 100%, 75%, 50%, 25%, 0 (clear).
Set passcode on a per notebook basis.
Move selected elements to different layers, pages, or notebooks.