For me it's being able to pick and choose the resistance to button presses, I go with heavy (60-70g) springs because I have a habit of hammering on keys and that resistance reduces the time I spend bottoming out the keys.

I use tactile switches (no audible click but a noticeable feel of when the switch actuates) instead of the 'blue' or clicky keyswitches because I prefer my keyboard not announce itself.

Linear switches are also an option, with some of them you can have an entirely silent action, often with softer springs so that typing on it feels like brushing your fingers across a cloud (for me softer springs means pressing random keys all the time because I am a ham fisted gorilla in a human suit.)