I have this TV, and what I can say is that the picture quality is outstanding! I cannot say I've seen better picture quality on any other set. (however I have not seen the new range of Panasonic Vieras)
I have Sky HD hooked up and its looks amazing, crisp, detailed, vivid colours, you really can see the difference! I must also add that a normal SD sky box looked pretty good too, I know this as I didn't have Sky HD at the time of purchase
in response to the previous reviewer, I have also connected my Xbox 360 via HDMI, I must admit it did seem slow to react, that was until I looked through the menu's (which are easy to use) and I came across a game mode, once I had turned on Game Mode, the Screen was perfect to react, was very responsive, and the image quality was also brilliant!
However, if you would like to use the internet widgets feature, you will need to buy a separate Samsung wireless adapter as there is not one built in and it doesn't come in the box!