I got mine a week ago from my wife, it was a gift. I also own a GP XD. I have a couple of issues with my device. Start button works when it wants, it doesn't register the input everytime. DPAD is pretty bad, I play fighting games and is quite terrible for it, also sometimes get stucked, so I have to play most emulators with analog.
Performance is quite similat to GPD XD, in some android games run a bit better, in other games is laggy, like asphalt 8, asphalt xtreme, or riptide GP:Renegade. Those games are smoother in GPD XD. In emulators performance is worse than GPD XD. Uoyabause runs slow, even in 2d games like Story of Thor 2, which is fullspeed in GPD XD. PPSSPP performance is also worse, is impossible for me for example to play Tekken 6 at decent speed, in my GPD XD is full speed.
Google play Store also shows less apps than GPD XD, though that's probably because I use legacayrom in GPDXD. Would be nice a legacyrom for this JXD.
All in all device is not bad, but I personally prefer GPD XD. If it weren't because my wife bought it for me I wouldn't have bought, because is not worth the price.