What are you thoughts on KOReader?

KOReader is a document viewer for E Ink devices. Supported fileformats include EPUB, PDF, DjVu, XPS, CBT, CBZ, FB2, PDB, TXT, HTML, RTF, CHM, DOC, MOBI and ZIP files. It’s available for Kindle, Kobo, PocketBook, Android and desktop Linux.

What do you think about it? Is it privacy-focused/privacy-focused? Are there any better alternatives beside PDFViewer?