I even wrote a script to automatically calculate the mud server "processing" time
(by walking on civilized terrain). The slowdown was obvious when lots of ppl (20+)
were on.
Note that you can't determine this by ping as Carrock wrote. Ping will give you
network roundtrip time between your machine and the Linux (I assume) kernel
on the box that CF runs on. The CF process could still be affected by load on the box
or load caused by itself and this will manifest as a slowdown or sluggish feel to you
when you play, but won't see anything abnormal in ping.