I think up to 32" would be good for UHD.

Anything over 32'' has its place in a work environment, instead of having 2 or more screens you have lets say a 36 to 40 one that acts like a fusion of 4 monitors. On a sidenode... if anyone got a desk job and only one monitor (FHD)... go complain... that's unacceptable^^

Imo too small for 4k. This size is more appropriate for 1440p.

Bah. The increased pixel density is great as long as apps properly scale UI elements. In games you'd hardly need any anti-aliasing with such high pixel density, and you'd be able to see finer details like individual leafs of trees in games.