I own a JT-B1 since August 2013 and it has the following issues:
1.  Screen visibility is really poor when viewed sideways
2.  A LOT of audio noise when recording video...  I was in a quiet environment, with traffic noise very light, and upon playback, there were whistling/scratching noises that were generated by the recorder.  I recorded the session, side by side with a iPad, and the iPad reproduced what I actually heard.  Light traffic noise was NOT captured by the JT-B1 due to the "noise."
3.  When placing the unit at a window to record timed-lapse photography, the unit would constantly focus, and refocus, thus causing momentary lapses in focusing
4.   WiFi sensitivity is truly terrible.  Occasionally, it would lose WiFi signal, while the iPad always had a steady signal.
5.   When originally purchased, it had no functional spell checker...   Oddly, every word I typed, (for example when emailing) it would "recommend" with the strangest people' s names, like "Adellaile, Rodolphus, etc..."  One of the subsequent Android patches fixed that. 
6.    Lot of freezups...  Occasionally also the unit refuses to power-up, where I had to plug it in for the light charge to come on, then I could power it on.  Also one time, it died on me with approx. 70% charge.  Tried to start it up, and nothing.  I plugged it in, managed to start it, but then it died again.  This happened a number of times.  I let it charge for a while, then turned it on and saw a less than 10% charge.  What happened, it mysteriously lost 70% of its power.  It never happened again, and I hope it was a firmware problem.
7.  The keyboard is tiny, and although I have small fingers, many times, I accidentally hit the status bar, beneath the space bar.  this happens when the unit is in its landscape orientation.  Less prone when it is in portrait mode.
8.  USB is eccentric.  Although, its visible, as an external drive, one cannot typically save directly in the unit.  It always works when saving a file in the PC (Windows XP-Pro SP/3) and then copy/paste in whatever directory you have created BEFOREHAND on the JT-B1, as it sometimes, refuses to create directories when done through a PC.
9.  "CamScanner" application from the Android store creates images and PDFs on the tablet.  They are visible and can be accessed through the tablet's "OI File Manager", but when connected via USB in a PC new files will NOT display!  I presume this may be the "CamScanner" problem, but why would new files appear in the tablet but not in the PC, when connected via USB?
10.  Screen orientation, takes about 1.9 seconds, which reduces the frustrated user to shake his/her hand like someone suffering from Parkinson's disease to make the tablet respond faster.

Very thorough
Very informative
The results of the gloved touchscreen test is a bit disappointing. But I must see for myself. I am definitely still interested in buying