Originally Posted by JSWolf
An unregistered Kindle is a very poor choice. You collections by not registering. Also, ePub is open when not encumbered with DRM. Mobi & KF8 are not open even if no DRM.
My understanding is KF8 is essentially the subset of ePub2/3 that the Kindle happens to support at the time, which is no worse than anybody else's ePub support, since nobody's is complete. It's annoying you have to 'compile' to KF8 from ePub, but it's pretty transparent since Calibre etc. can do it for you.