I got the DPT-RP1 2 months ago for my graduate studies. Despite all the known problems, one of the best gadgets I ever got.
It replaced my notebook completely and lots of papers as well. The lack of apps (compared to Ipad Pro/Surface etc.) is a feature for me as the device focuses on its strengths and limits distractions for me. It is way more convenient to take to meetings than any other electronic device. Reading is perfect (and no comparison to any non-e-paper device) and note taking works well too. Had no problem with the app so far (on windows). My only cons are the high price and build quality (does not really feel like a "premium" device, don't know if it holds for many years).
Would highly recommend the device (RP1/CP1 - whatever size desired) for anyone who needs to read a lot of papers / take a lot of notes and doesn't mind the high price.