Just got a 4K....
I have to say that what I have seen I have been blown away with the TV I got at Christmas. I was sort of lucky to get the Bang & Olufsen Avant 55 - 4k TV - and surround setup. It hasn't got the HDEC chip but other than that its jaw-dropping. The first thing I watched was the ULTRA HD 4k transformers youtube trailer and everyone that has seen it was very impressed. I haven't seen anything so good in a long time and have always had the home cinema bug. I brought 8000 DVD and about 1000 blu-rays. I have started to rewatch the blue-rays as the TV does a very good job of upscaling the 1080P.
I am pissed at the lack of 4k content as watching some GoPro videos or rain drops over a wonderful sunset does tend to be boring. Christmas morning was a 4k fireplace :)
The TV (it also moves every time it turns off) makes me smile every single time I turn it on or off and a piece of technology that does that before I have even started to watch anything is a good purchase.