I've had mine for 4-6 weeks now. I'm not returning it, but I can't particularly recommend it - both the annotation and eReading experiences are significantly inferior to what you'd get with Onenote, Notability, or Drawboard on iPad/Surface.
The reMarkable hardware is nice, but its stock software is frankly disappointing. The hackability is a "plus", but I don't want to have to resort to unsupported firmware tweaks to fix a $500 device.
Specific feedback:
* Zooming is incredibly coarse. There is no pinch zoom, only a button in the UI that jumps in intervals of 100% or more. On many of my documents it goes from slightly too small to WAY too big with no level in between
* Speaking of zooming, the pen controls overlay the document, often blocking parts of the text. There is no way to scale the document to fit in the remaining space. There's not even a way to have the button backgrounds be transparent so you could still read most of the text.
* It doesn't support in-document hyperlinks in PDF or ePub, so your table of contents and index are worthless.
* If you somehow know what page you want to jump to, that's buried two menus deep and frustrating to get to
* Search is very slow in large (100+ page) documents, and results trickle in gradually so you can never be quite sure when you're looking at the whole list. Given that one of my desired uses for the device is to carry around some PDF textbook-style references, this hurts.
* You can't change the default writing utensil, so if you don't like the grainy mid-width pencil you have to change it every single time you open a new document
* There's no pressure sensitivity in the pen
* The eraser works like a pencil eraser, not a digital one. There is no way to erase a stroke, so you'll inevitably erase more than you want to and have to redraw some of it