Lenovo Flex 5.
1) The pen colour swatches in the top display need a border for contrast. At any but a perfect viewing angle, the black pen blends in completely to the charcoal background.
2) The eraser functionality is unpredictable and frustrating. A long press of the eraser button on my pen will permanently change the tool to eraser, requiring I make a large movement to change back to pen tool. It appears to be inconsistent in whether it changes tool or just erases that line. Please just make this a checkbox option and make the behaviour consistent; option 1 being erase only when holding button, option 2 to have the button rotate to the next tool. To be extra awesome, be able to select which tools are in the rotation (pen and highlighter, pencil and eraser, etc).
I would also really really appreciate any increased control over pen behaviour. I understand a full blown pressure curve might be too much to implement, but at least a minimum and maximum slider.