Edit: In german version this feature is HIDDEN (like explained below), in other language versions it seems to be SHOWN (confirmed: french and english)!?
Maybe some of you know this already, but to me it was totally new that MobiReader (PC) already supports ePUB!
Just klick on IMPORT and select "all supported formats" and though it's not shown individually - like all the other formats - you can see and choose ePUB files. Imports nicely and works like a charm (with cover and all)!!!
(Just one minor bug: If the language is not set in the ePUB file you need to add this to the OPF file inside the ePUB archive (ZIP) or it won't import the file! I used DEU for German and ENG for English.)
As I convert all my eBooks to PRC before using them on the CyBook, this is a BIG plus for me and makes the support for ePUB with the new firmware release simply useless for me...