I am currently leaning towards buying the EZ Reader version of the BeBook next spring. There are things I like about both the Cybook and Bebook/EZ Reader but...
1) I live in Washington state so dealing directly with a company in California for warrenty work, parts, etc. is much more appealing than going through Books On Board to deal with a company in France. Dealing directly with BeBook in the Netherlands would eliminate the middle man, but there would be other types of issues (time zones for one).
2) I can get a battery for the EZ Reader/BeBook at any cell phone supply place for $10 or less and install it myself. I really like this part because the Cybook battery is $45 + shipping directly from Bookeen.
3) After having a iPod with just the wheel for going through menus, I want the number buttons to make things easier even though they clutter the device a bit. I also like the location of the page turn buttons on the left-hand side.
4) I like how many formats are available on the EZ Reader/BeBook and that I have the option to load other reader software. I likely won't, but the having the option gives me warm fuzzy feelings.
Cybook just doesn't seem to be quite as accomodating for loading other software as the EZ Reader/BeBook from what I have read.
5) The US prices I would pay for a Cybook or BeBook are the same, about $350 + shipping for the package deal. I hope that by spring the EZ Reader will have the shipping from China to the US issue resolved so the price will go down a bit from the current $324 + shipping. Also by then the Mobipocket support for all Jinke V3 devices should hopefully improve.
Many of my reasons will of course not apply to anyone outside the US and maybe not even on the east coast of the US, but hopefully they might provide you with a few things to consider.