I emailed Kobo regarding the wasted screen real estate in 2.5.2 and suggested they take a look at the posts in this forum to gauge their customers' reactions. I also mentioned that because Kobo is known for offering flexible reading options, I was requesting that Kobo implement a full-screen reading mode. Their response was, in part: "You said that you would like for your device to have the option that enables you to read in full screen mode. This feature request has been sent to our feedback department to make note of."
This seems a reasonable first response, and I suggest that others, like me, who want the option of using the entire screen for actual reading, should email Kobo to ask for it. Perhaps if Kobo gets enough direct requests, they will implement it.
I used
feedback@kobo.com but the reply came from
help@kobobooks.com. I imagine either one of those email addresses would work.