Well, I spent a while trying to get the M96 to work for me, and I found it just too fussy. I'm planning to return it. Not because of any of the firmware issues -- that was a very simple matter.
The problem is that Android is just not designed to do what the device is capable of/limited to. The M96 offers the illusion of great potential (Google Play apps, Bluetooth support, etc.) but the execution of these other features is marred, usually by no fault of the device itself.
It was unpredictable to figure out what the various buttons and joystick would do in different apps. Touch gestures via the stylus are awkward when they work at all. Many apps are simply not functional with the e-ink screen, which is a shame. Handwriting input works well in the NeoReader and OScribble apps, but the closed ecosystem of the reader itself makes it too annoying to get those annotations in and out to other programs.
By contrast, I got the rare chance to spend some time with the Sony DPT-S1. Someone in my office has one and let me borrow it for a day or two. The Sony is far more elegant and polished. It is limited in its functionality, but flawless for actually performing that function. It does one thing and does it superbly well.