I have a Remarkable tablet which I think is the only direct competitor to Sony's writable e-paper tablets. It's really jank! That's to be expected of early adoption. But also, it's nice to use. I love taking math notes in it.

The main stat for these products is the pen latency. Sony's previous product, the DPT-RP1, according to reviews, had worse latency than the Remarkable, which to me is only noticeable if I make a fast stroke and look for it. I don't have any official numbers from Sony though.

I'm watching this space as it develops. I preordered the Remarkable which took a lot off its price tag-- I wouldn't buy any of these devices at their current price points. They would need to be much more polished. A lot of that is on the software side, so such a device with an open, supported platform would be quite exciting.