Are you still staying with 4.4? That is what I switched mine to shortly after receiving it but just watched a demo video (not in English, of course!) of the 5.4 software and was reasonably impressed. My main concern is that I like the built in reader in 4.4 and am curious about the one in 5.4.
Was in contact with Pocketbook a few weeks ago and they are now saying September for the release of the next software update.
Also looked at a video review of the Onyx Boox i86 due out later this month in England and was very impressed with it using Android 4.0.4 with an update to 4.4 due soon after its release. It appears to be 15 mm longer, 2 mm wider, and 3 mm deeper than the 840. There is a silent video that demos both units side by side.
http://blog.the-ebook-reader.com/201...parison-video/