Well, I did post some impressions in the meantime
over in this thread in the german forum but sadly haven't got the time to translate all of this for posting it over here too.
ArtaTech send an answer on July 21. and offered to take back the device. A solution for the IMEI-problem was not given. I did expect not much more than this but as the phone-functions still work alright I will keep it.
A review has appeared on
onyx-boox.com which sums up things quite good. My experiences with the battery are basically the same.
So, it's nice as a mini eInk-android-ereader and the phone-functions are a neat extra but this concept won't hit home on the market. For most people looking for something similar (eInk, phone, small screen) a cover-ereader of sorts as an extra to a normal phone will be a far better solution.