The Pen functionality and apparent ease along with the design and size of this e-ink based device does look promising and is hitting alot of the right marks however the locked down nature of the device as others have said make it a tough sell purely as a note-taker.
I recently tried an ipad pro 9.7 with apple pencil and the charging and pairing become quite annoying with heavy use,also i hated the feel of the slippery plastic of the pencil so it was an all-round negative experience.
I could see myself buying this but if they do insist on keeping the OS locked it MUST also be a decent ereader that offers similar functionality to the kindle/kobo.
With Onyx already showing off the same 10.3" display from Eink with Android reMarkable are going to have a tough sell on their hands even if there Pen input is slightly better.
EDIT: The 55ms seems pretty impressive and i wonder if this is apart of the new e ink regal waveforms that have been hinted at for ages,current carta screens refresh at 120ms i believe so this is quite a substantial improvement,unfortunately it's still not enough to smoothly playback standard 24fps video though,perhaps i.mx 7 will push the latency down even further