I received my Cybook this morning and have been comparing it to my Sony 505. Both are beautiful in their own way. I really like the feel of the 505, the weight, brushed metal, and case. The Cybook's support of Mobipocket and the ability to do a dictionary lookup forced my hand.
The button to turn the pages on the Cybook is hard to get used to. I think the unit is slightly defective - it takes more force than it should. (BTW, I e-mailed customer support and they were extremely responsive. I may return the unit).
The leather case for the Cybook bugs me. The magnets don't stick so it kind of flops open. I can't imagine not using a case of some kind.
When I first turned the unit on I thought the Cybook display was better than the 505. I may be imagining things but In natural light the Cybook looks better. At best they are very similar. When I figure out how to load more fonts the edge will go to the Cybook.
The fact that the Cybook is easily recognized by my PC and it's a piece of cake to transfer books is a great plus.
I plan to deck out the family with Cybooks so I can forget about the hassles of converting LIT files, etc. and standardizing on the Mobipocket platform (via Fictionwise of course ). Viva La France!