- while the total resolution is slightly higher on the RMPP (229 PPI) compared to RM 1/2 (226 PPI), the effective resolution is lower, especially for ebooks/PDFs. When you have text on say grey background you can barely read the text on the RMPP while there is no problem on RM 1/2.
- starting with RMPP there is coil whining (not loud but you hear it in quite settings)
- while the advertising sais "Can render 20,000 colors", you have actually a very limited number of colors when it comes to one pixel. Colorful images or highlighted text is being rendered quite coarsly as on those cheap 7-color e-ink devices (but faster and with higher resolution)
- you can't use the (quiet expensive) pen which works for RM 1/2
- the software feels quite unfinished in a lot of aspects. This is hard to summarize of course but includes very slow processing of and poor interaction with ebooks/pdfs or the close to non-existing integration of typed text.
- without the cloud it's hard to get documents on your device. The web interface is fiddly and for some documents it simply doesn't work.
On the plus side you get root access on a relatively native Linux system and there is a community providing cool stuff [0]