I bought the GPD XD off eBay, was great for about 24 hours, then the battery went from 80% to nothing and powered off, then refused to charge. Apparently it's uncommon, but has happened to other GPD XDs out in the wild. I opted for a refund instead of a swap. It's probably very uncommon, but one bitten, etc etc.
Issue documented by someone else here: http://boards.dingoonity.org/gpd-android-devices/gpd-xd-no-response-not-turning-on-no-lights-nothing/45/
I was asked by the seller to video the issue: Did so here: https://www.youtube.com/watch?v=T6HXLLoBjvw
I bought the S192 Singularity and was a bit PO'd I couldn't just install the games on the promo pics like Portal, Trine2 and Half Life 2 from the play store. I then installed the firmware updates via links in the JXD Facebook page - https://mega.nz/#F!Ewp2FQgD!_4ThgwYYR8oiwwl0mbsH6w
- and rooted the device. This allowed me to write to SD (after installing SD FIX *root* (Kitkat issue)) (Use Kingo Root APK, not the root tool they give you...)
I then installed the games I wasn't able to via the Play Store via play.mob.org - definitely not legal, however I don't feel guilty since I already own these games on both Steam and Good Old Games (OK, I bought games on special without checking if I had them already... damn the Steam Sales
). I also installed Happy Chick to fulfill most of my emulation needs and then some other emus where I wasn't happy with how Happy Chick handled certain games (PSP games mainly). The device performs beautifully in game. Flawlessly. Grand Theft Auto Vice City, San Andreas, etc are smooth, fast and beautiful. A Bard's Tale w the HD Graphics, so fun.
Kitkat is an old OS, so navigation and interfaces are ok, but it's not "buttery smooth" like more modern OS's. Games work bloody great, very happy. Many games without native gamepad support can be played using controls by pressing and holding Start for 4 seconds and assigning controls to touch points on screen. For Castle Of Illusion this works really well. Games which rely heavily on touch... well... touch the screen, it still works fine.
Getting it how I like it was a bit of a clustermuck, so bear that in mind if you're novice or plan to give it someone who's a novice without doing some prep work on the device first.
I also found Smart Launcher Pro is better to navigate than the generic launcher, automatically categorises games, multimedia, internet, comms, utilities and settings.
Personally I found the GPD smaller than I'd like as I have big hands (You know what they say about big hands... big gloves!) and below average eyesight. Having said that, the GPD XD can be folded up and carried in your pocket, the JXD S192 certainly cannot.
Hope this helps :-)