These are people who can’t stop noticing both the ham-handed flaws and clever tricks in the design of every piece of software they use. They live breathe, sleep, and dream product design. Sometimes they come from an engineering background, other times a design background: the best ones have both. They spend their time thinking about the nuances of interfaces — about simplification, information architecture, etc. Sometimes they have academic experience in HCI, but more often they picked up their instincts building real interfaces used by millions of people.
