I went to AC inbox - opened some messages, filled scrips and saw instantaneous blips on the cpu usage from 4-30%, opened a note an saved and saw instantaneous blips of up to 50% (all on my server), but these are instantaneous and other people are using my server also. I am not sure this is a "real" delay - it is still relatively instantaneous when I do this - no real pause.
When I run my filezilla downloading program I get a longer jump up to 30-40% and when I open AC for the first time I get 1-40% as it does each of its steps to run - my server runs 1-10% just at idle (other computers accessing it).
I am not sure that using the CPU usage meter really means a lot - I think it is like our brain - some tasks turn it on and use it for a bit, while others we do without thinking (often that is talking without thinking.....).
Just my thoughts.