Loads of them in books sold through Watersones.
The worst being China Mieville's 'Perdito Street Station' in which whole chunks of the book had been randomly duplicated throughout the text making it effectively unreadable. And their conversion of 'Voices' by Arnaldur Indriðason is poor - okay they're having to deal with Icelandic names and places, but Unicode supports Icelandic characters. The book has them all correct and present, in the eBook they are missing or completely incorrect ones substituted. If I was an author I would be furious at the way my work was being treated.
Waterstones don't want to know about bad conversions, you'll have to fight to get your money back.
So far nothing wrong with Kindle titles, but I've heard of some titles having an eccentric approach to page setting and spelling.