I have used the Android beta on the Samsung S8 and on the Yoga book, as well as on the Samsung Chromebook plus. Installation and the initial sync were without problems. However, after annotating pdfs I lost the annotations once or twice completely. It is great that one can manipulate folders, but I was surprised that folder deletion happens without further confirmation, which could potentially cause serious headaches.
The Android beta worked stable on Samsung S8, but I had several crashes on the Chromebook plus. Using the pen as input device during pdf annotation is not the smooth experience that I had hoped for (no palm rejection for example). The lines look smooth in the paperpile pdf viewer, but edgy when looked at with other pdf viewers.
Anyway, it is awesome to finally have this app, and be able to read through my papers anytime anywhere. Keep up the good work!