My three choices would be:
1. Annotations bug. They seem to work okay with .kepub so fix them with .epub.
2. Fewer regression errors -- the one where they fix a bug and then another bug fix/code change resurrects the older bug. OTOH, I spent much of the Windows 95 beta complaining about the same thing. Some things just don't change.
3. Fewer reproducible bugs surviving through multiple firmware revisions.
Regards,
David