Hi. I'm the main developer for Madshelf. Many people have been clamoring for a delete function (I have no use for it myself, but it seems a popular request), so I'm glad you like it. If you have any other feature requests, let me know. As for cybook support, it is in progress and already quite far along (Madshelf is ready, the rest of OI nearly so).
As for the question "why would I want to [install OI on Cybook]?", the answer is simple: because soon it will do everything that cybook's firmware does and more, and the things that cybook's firmware already does, OI will do better. That, and it's open, so it is fully customizable. So the question will soon be:
Why would I keep cybook's limited original firmware?