The Sony Reader is tied into Sony in the same way that the Kindle is tied in to Amazon, so your reasons for being dubious about the Kindle would apply to that too.
Don't know a lot about the Cybook and it's file reading abilities, but from the point of view ergonomics, the EZ Reader has two sets of buttons for turning the page, which increases the ways you can hold it and in which hand. The screens are identical.
I notice that the EZ Reader doesn't mention that it reads Mobipocket files. This is odd, because the Bebook (a European version of the same Hanlin V3 device) certainly does. But different companies rebrand the same device and then produce their own software, and maybe they haven't got a license to do Mobipocket yet. Definitely worth finding out for sure before buying. It's actually very easy to install any of the different versions of the V3 software, so you could run the EZ Reader with the Bebook software, but you may not want to go down that road!
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