I have a Remarkable 2 and I would say is not that good at reading PDF documents or ebook files (mobi, & epub). Very slow at loading documents and moving forth and back between pages is worse when compared to a Kindle. Remarkable 2 strength is mainly focus on creating notes to read.
I had a remarkable 1 that I used primarily to read epub/pdf and my enduring memory was how slow it was to wsitch pages. Realise this is mostly a hardware limitation of the screen, but I found it frustrating. With some sadness I went to an iPad pro 12.9 which was very fast to switch pages, and I don't have that same sense of frustration.
