I played with Kobo Glo in the shop and was quite impressed. Cannot recommend though as I don't have enough experience with it. I did order and return Odyssey - mine unfortunately developed pinholes through which light was shining. I did not hear about anyone else whose Cybook would have this problem.
It is (Odyssey) a very nice device, screen is lighted well, many options and interface will be familiar to you coming from Gen3. Something to consider as you cannot have folders on Kobo. I confirm you can turn off the light completely on Odyssey. When light is off the screen seemed quite dark, darker than my vizplex Opus or Pearl on K3. I didn't like it (please remember my opinion is totally subjective, perhaps for you it will be all right) I never read PDF on ereaders so was not even interested in trying that feature.