UI is important, learn to know what good or bad

UI is the second most important part of any application or service.The service or function is more important, but it's not important at all if users can't use it.

How to know whats good or bad? Thankfully, our old friend Cognitive Psychology provides us with the key. Just record a user using your UI (or use it yourself and make notes).

Every negative counts twice, that's how humans perceive negative impact.

The higher the score, the better it is.

Of course, this is only generally true, performing 200 actions to change a song on your MP3 player is not a good UI. Even if every step was intuitive.