I swear you guys need to get your eyes checked, have you even compared the screens yourself in the flesh or at least checked any of the videos I linked. Its as clear as day and night the difference in quality.
I have no doubt that you can see a difference if you stand close. I'm disputing that the difference is noticeable at a normal viewing distance. Measure how far you sit from your current TV, and then next time you go to the showroom compare the TVs while standing at that distance.
I watched the video you posted. I agree that it showed the text was clearer on the 4K panel, but I wouldn't have been able to read that text on either screen from couch distance.
For the other comparison he said that the colour looked better on the 4K set, which shouldn't have anything to do with resolution. That means that either the 4K TV had a wider colour gamut (i.e. it can reproduce more colours), or the two sets were not calibrated the same. If it is the former then that is a good advertisement for wide colour gamut TVs If it is the latter, then the comparison is meaningless.
So just to be clear: I'm saying that for most people an upgrade to 4K is pointless unless they're also upgrading to a much larger TV. The 55" 4K TVs are at the borderline where you might notice the difference if you were sitting at ~ 2 meters. It is the larger size sets where 4K shines, and it isn't as clear to me that they will see the same wide adoption.