Works with the latest firmware of december 2014 on an Odyssey HD frontlight.
If you want to get rid of the advertising in the library of the home page do as follow :
Connect your Odyssey HD to usb as storage.
Open Cybook usb hard drive.
Go to the folder system/user/store
And delete a file named like : "estore_[cybook] Bookeen Store .thx"
That all, of course next time you will connect to wifi the advertising will come back.
The folder system is hidden by default, so you will have to unhide it.
You could use Mu commander to do that :
http://www.mucommander.com/