In test, with two TVs side by side one at 4k and 1080p and at an appropriate viewing distance, and taking into account the retinal theory concept that the eye cannot percieve a sharper image at a set distance, the results show that for some source materials you can tell the difference between 4k and 1080p.Now a screen size less than 48 inch is pointless for 4k in that respect. But it is also about your visual acuity.Some people are better at picking out details than others.
If you can afford a 4k oled then yes you have the best TV money can buy.
I personally feel that with 4k our viewing habit changes so we will be sitting closer and will enjoy the details 4k will bring.
I recently brought a 4k 60hz on a displayport 1.3 connection, a Samsung 28inch TN monitor with 1 msec refresh rate and with my Benq 1080p monitor on the same desk I could tell the difference with the same working distance and prefer the Samsung in one sense;sharpness was astounding at that proximity.
As it is a TN panel but tweaked to deliver 1 billion colours it does lose the contrast of the Benq VA 1080p panel.
But a true 10 bit Ips grade 4k 60hz monitor will cost £800.That is too much.
It is a 'trial' way into 4k.But I am glued to my desk and not my couch.