4K is already useful...

[Visionist]

...for people like me who sit close to their screen. I sit 5.5' from a 50" screen, and sampling Avatar's final battle (in 2D) I decided to move as close as 3' for a more immersive experience. I could not resolve individual pixels at that distance, but the picture quality obviously wasn't up to par, and the experiment was a failure. The same footage upscaled on a 4K display would have completely eliminated that "I can almost see the pixels and it's distracting me" issue.

...I think

Obviously most people don't sit 3' from their screen, but I'd like to be able to sit 7 or 8' from a 65"-80" screen and upscaled 4K is surely a good idea in that case?