I can't replicate those results either, Nigol. I went from 1.9.2 to 1.9.4.
Now... on a side note. I am wondering if anyone experiences very very very slight ghosting despite full screen refreshes? For instance, it is most noticable when in a book and returning to the home screen. On the greyer shades of book covers, text from the previous screen can be seen very faintly. Also, when entering the Books list from the home screen, even after a full refresh the old page can be seen very faintly on the white background.
It is so faint that I believe it must be the way that the technology works, although I didn't see this on the older Kobo (or so I don't think). I also don't think I saw this on a Kindle, although maybe I was mistaken.