Just checking back in to let you guys know that i've tested my unit for about 45 minutes on an Xbox 360 through HDMI at 1080p. I am VERY happy to report that I experienced none of the issues you listed in you posting OP. My unit's picture was impecable to be quite honest.
The colors were crisp and clear with no tearing or juddering of any kind. I tested the unit by first just navigating the 360's dashboard and then by booting up Skyrim which looked outstanding if maybe a little bit dark as you reported but that can be adjusted quite easily.
I played skyrim for around 20 minutes looking for any signs of a bad picture with nothing to report. The only issue I had was that because of the 200Hz all of the movement seemed sped up and faster/smoother than normal but you can adjust this as well I just did not have time to fiddle with any of the menu's.
I then exited the game and put on a 10 minute HD video that I had installed on the xbox and was once again extremely pleased with the results. Whites popped and faded to black seamlessly and I was happy to notice that their was very little backlight bleed around the corners which is a known issue with many edge lit LED tv's.
This video once again played through without a hitch. No jumping, juddering, flashing, or tearing to report.
The next test on the list was an extremely high pace game of Pac Man Evolved CE 2. This game can prove a test for any tv because of the high pace of the game and rapidly changing colors as many could attest to. This was played for the remainder of the 40 minute in whole adventure of mine. Once again i was happy to notice there was ZERO ghosting that I could notice.
Over all the TV seemed very sharp. The frame is nice, the bezel is very thing compared to my old Sony and Sammy. Their was little to no light bleed and the response time was extremely low, I certainly didn't notice any input lag even in Pac Man which is a very speedy quick reflex game.
Now I did not get to try this tv hooked up to my virgin media cable box but I cannot see why that would cause the picture to degrade any since it will be through HDMI as well. I also unfortunately did not et to test the 3D mode either because I'm still waiting on my set of glasses to come in the mail lol.
I wish I had more time to give a proper review after playing with the settings and maybe doing a color test but from what I could see in quick rundown with my own two eyes, this TV is an absolute STEAL at the price even without the 3D.
I'm sorry to hear your having issues with your set though and I would think about getting it exchanged just so you can try another unit and try to narrow the problems down.
best of luck mate I really hope everything works out for you in the end.