At first you don't necessarily know what's wrong - just that something is a bit 'off'. As you troubleshoot, you learn what each little vibration relates to. Things you'd never feel with stock rubber mounts.
It's like listening to a symphony - you may not know every individual instrument at first, but as you listen, and each section drops in and out, you learn what sound comes from which instrument...except it's an engine, and it's vibrations, not sounds.
It's a fun learning process.