Do you have any thoughts on providing manually pre-formatted PDF files? Em-dashes, curly quotes, etc. are all nice, it's a step in the right direction, but in the end the EPUB file needs to be interpreted by the ebook reader on the fly and in terms of typesetting quality the outcome is far from what physical books provide, since you still get orphans, weird hyphenations, ugly/misaligned chapter titles. For me, nothing beats reading a print-ready PDF file.