I have one (DPT-S1) for years after a kindle DX screen felt too small, and still use it for reading technical papers and books. Papers are a pleasure to read. The weight is light-feather. The price was extravaganza-level but haven't repented, I love this gadget. It synchronizes via web-dav with (for me) a box.com account, perhaps slowly. Is a superb reading device, battery lasts more than a week. Is not a tablet, web browising is enough for landing in a specific blog post or wikipedia article, but anything cpu consuming will be slow. After the years the stylus cilindrical holder came apart. The writing experience is functional, but lags to a point compared with pen and pencil (but is workable). Mine has SD-card with 32 gigs. Page flip on scanned books makes you wait. The software is minimalist but not buggy. No sound.
TL;DR: Better size for reading paper-oriented PDFs than reMarkable. Nice hardware. PDF software works well. The app for getting PDFs onto the device and its telemetry terms are bad (or at least were when I bought the device). Does nothing other than PDFs. Annotations are saved in the PDF itsel and move with the PDF to a PC.