If I use a terminal with 30msec latency to connect to a host with another 30msec network latency, it's now 60msec - pretty noticible by an average human being.

If I use a terminal with 30msec latency to connect to a host with another 30msec network latency, it's now 60msec - pretty noticible by an average human being. That's why reducing latency where you can to the minimal possible value is important.