With my fingers crossed, I'm putting out Bookcase 0.7.1. The encoding issue was that opened files were being read as being in the user's locale, rather than UTF-8. Note to self: QDomDocument::setContent(QString, ...) is not the ticket, QDomDocument::setContents(QIODevice*, ...) works much better. And if you overwrote a document file with the double encoding, you can fix it by using the iconv command:
iconv -f utf-8 oldfile > newfilefor each time the document was saved.
Along with the encoding fix, there were a couple other bugs to fix. Bookcase now compiles with GCC 2.96. The fields editor now truly sets the field title, and bibtex and CSV export will always be in the user's locale, rather than UTF-8.
As always, who knows what stupid error snuck in. Backing up your data before using a new version is probably a good idea. And remember, no guarantees! :-)