i went through this decision recently. i really wanted an e-ink device as i get eyestrain on my computer, and i seriously looked at the kindle, the sony 505 and only learned of the cybook on this board.
what decided me is that i looked at formats and what books were available - the cybook reads mobipocket plus several more formats, and you can easily convert all sorts of formats to mobi using mobipocket creator. and if my device needed repair or i lost it, i could still read mobipocket files on my computer in the free mobipocket reader (a great program, btw) or could read them on a handheld. and that's part of what decided me - that if my reader were unavailable, i could still read all the books i had downloaded and paid for. i believe that would not be the case with a kindle or sony 505, although i could well be wrong.
and i must say that i love my cybook
