Got my cf-19 yesterday, cheapest mk6 I could find on ebay and it's not too bad. Has 5360 hours on it and looks great. Couple pressure spots and a bright pixel but that doesn't bother me for the price. Its a CF-191dyc51m, has GPS and everything works.
I couldn't find much information on installing windows 10 on the mk-6 so I figured I would give it a shot. I used the free upgrade (on screen keyboard is assistive technologies right?)
So far everything works great, had to make one small change to the settings, I selected to disable the touch when the pen is being used as this would cause the pen to be jumpy. Also uninstalled the panasonic bluetooth software as the windows bluetooth support is pretty good. All the other Panasonic software seems to work as designed
I figured out a cool trick with the GPS. Since our GPS chip is com based it is only in use when a program accesses the com port. windows 10 added integration of GPS systems like a phone where the GPS is there for any program to use. I found a piece of software that pulls the GPS data from the com port and translates that to windows 10 sensor data. Now the GPS works like a phone where you can enable and disable it by turning location on and off. This allows you to use windows (bing) maps with turn by turn navigation. Also google maps on chrome works, as does any other website that can pull location. http://www.turboirc.com/gps7/
Verified today that the verizon card works perfect. Windows can connect and disconnect with no extra software.
As others have also noticed, screen brightness is a little different. I can get as low as %3 but as soon as I drop below that the backlight turns off. This is fine for me and I have no issues. Also the light sensor works fine and automatically adjusts the screen if you chose to enable that option.