Switching pages can still take a few seconds (the display is lightning fast, but the processor for generating the page is not).
Can take up to a few seconds, but really depends on what the device is rendering. For most arXiv papers and light graphics (e.g. clean charts) the page turns have been very tolerable.
Exactly. I have one and I think writing has really short latency. My friend says it's slightly slower than an iPad but I haven't tried that so I don't know, in any case it's still very good.
The only really bad thing about the reMarkable is that the software still sometimes crashes, leaving you for ~20 seconds with a notebook that you can't write on.
Interesting, in 3 months I haven't had a single crash
In practice, it's been perfectly usable (for me). The only nit I've found responsiveness-wise so far is the startup time. It's not convenient when I suddenly remember something and want to write it down and have to hold down the power button for three seconds and then wait another five or more for it to get to the main screen and then wait another two or so to get to my scratch pad.
Maybe it's just time for me to update? I bought this in 2014.