That's all changed now. I'd love to know why it's changed. My first thought was publisher pressure. But Kobo hasn't implemented harsh measures. Just Amazon has.
At any rate, I'm now using Kobo for my reading. Easy to break DRM. And they don't assume the same level of control over Kobo ereaders the way Amazon does with Kindle. I have over a thousand ebooks. I'm able to tag books in Calibre, and those tags automatically show up as Collections on the Kobo. It's a simple thing, but Amazon never gave me such flexibility. Makes a huge difference for me.
It's also possible to alter Kobo's UI/UX with various plugins without the need to jailbreak. Kobo (the company) is perfectly happy to let you do whatever you want with your own device. That's such a breath of fresh air compared to how Kindle is locked down.
All seamlessly, because Kindle used the cellular network for reading progress. Really a magical experience.
Then they removed cellular and _buttons_ from the devices. And now their app is actively crashing on my Kindle when I try to use it to buy a book.
I'm either old and stubborn or principled, but I want to use my current phone and "system" I've been using to read ebooks for the last 15 years.
(It's possible that kindle unlimited is a cheap enough system to make dealing with amazon software, but amazon is annoying enough that so far nothing has convinced me to buy into it)
But the main problem is that they don't sync the "last read" bookmarks until you open a book. But since that book didn't have a bookmark, it's reset to the beginning and then synced, so my "last read" bookmark is now at the beginning.
I've never experienced issues with them that break the reading experience. The one issue I occasionally run into is that the book progress doesn't sync when I open the app and I have to click "sync now" which sometimes is blazingly fast and sometimes takes like a minute.
I can't imagine migrating away from Kindle now, it's probably one of my favourite devices and the Kindle is my favourite way to read.