I'm not sure what the status of drm circumvention for fair/own use is in the US - I think there was a case that opened up for viewing/backing up dvds, but if not - this is still illegal, which partly defeats the purpose of buying through Amazon.
I always wondered if the kindle file was actually unencrypted.
https://arstechnica.com/information-technology/2010/07/court...
It can sometimes take a minute or two and sometimes it just hangs completely and you have to close the book and re-open it. I assume it's because it has to somehow render the whole book, to support the handwritten annotations and put them in correct places.
Though my main pain point is that you lose the book position syncing you get with the Kindle hardware/apps.