I have a Boox Note Air--it runs Android, and can do cool stuff to apps to make them work better on e-ink (mostly tweaking the contrast).
It's still kind of slow in practice, like all e-ink. Page turns will take longer than a tablet or of course a book.
It comes with a stylus, but the only note-taking app that works well with it is the built-in one, which is not great though at least it can sync your notes off the device. But standard Android apps that support pen input are unusable.
If you want to read PDFs on an e-ink screen, I think this is probably the best option. You need a much larger screen than Kindles have of course, and the Android ecosystem has some ok apps for PDFs and comics (the Boox has a decent PDF reader but I'd suggest using a different app that syncs).
When it comes down to it, though, I've never really been happy with e-ink. Tablets are just so much faster and more versatile, and for reading in the sun and so forth I'd rather just take a book.
I have Boox Note Air too, it is being used 70/30 as a note-taking device and tablet. It runs fastmail, k9mail, kindle app, firefox and wallabag just fine.
I wasn't trying to replace built-in note taking app, I think I may have gotten used to it? Honestly at this point I quite like it; it's fast (seriously, there is 0 lag when talking notes), it's capable and it honestly works just fine. I love the UI. I totally understand why you would want to replace it with one note or something like that - I'm just saying that current version works for me :).
I don't trust it yet however - I am using Onyx's sync servers, so my content is backed up without encryption to someone's else servers... Since we are talking about syncing - it also works with syncthing without any special integration; my notes are backed up immediately as pdfs on my other devices.
It is slow, if you think of it as a tablet. There are few options in "app optimizations" menu that allows you to switch between ghosting and page refresh speed.
I'm not sure if you can root it / if the bootloader is unlocked.
I'm using it with different stylus - the one from boox max - it doesn't have that magnetic lock, but it's larger and it feels like stylus tip has lower friction on the display.
I have a Boox Note Pro (small one) and I also find it great for taking big PDFs around for reading outside or while traveling. I recently found out about Onyx's GPL violations, though, which kind of sours me on the company and product. There's a discussion on reddit [0], a discussion about that thread on HN [1], and some other stories here and there about the issue as well [2].
Really cool to see a cheap e-ink android device but bummer that the company isn't compliant with the licenses of the open source software it uses.
I also own a Boox Air and I agree with everything you wrote. It is a device built for specific purposes. I get a ton of use from mine. It sits next to me all day for note taking, and I have my Kindle, Instapaper, and Safari Books apps for reading. I don't use it for anything else but that isn't the intent of the device. If you are looking for something all purpose, as you say, look for something other than eink.
It's still kind of slow in practice, like all e-ink. Page turns will take longer than a tablet or of course a book.
It comes with a stylus, but the only note-taking app that works well with it is the built-in one, which is not great though at least it can sync your notes off the device. But standard Android apps that support pen input are unusable.
If you want to read PDFs on an e-ink screen, I think this is probably the best option. You need a much larger screen than Kindles have of course, and the Android ecosystem has some ok apps for PDFs and comics (the Boox has a decent PDF reader but I'd suggest using a different app that syncs).
When it comes down to it, though, I've never really been happy with e-ink. Tablets are just so much faster and more versatile, and for reading in the sun and so forth I'd rather just take a book.