I never really compared the source to the converted mobi, but overall I can’t really complain.
Usually if the formatting is a little screwed up I assume it’s the source’s fault. :)

Almost every book I read nowadays is an epub converted to mobi.

Honestly, the bigger issue I have is the inability to put the sideloaded books into a series “folder”.
Instead I had to set Calibre to add “<series> <number> <book title>” string to the book tile in the metadata. :/

Pretty well written post.

On Kindle and epub: it’s pretty annoying, but once you set up Calibre to automatically convert on sending to device, it’s effortless.