"Why you should move that button 3px to the left"

Designers notice the gap between functional and delightful,
and that’s why we obsess over the little details. 
Getting design details right can create positive emotional states
that actually make products easier to use.
I came to realize that when a feature is 90% done from an engineering perspective,
it can still feel about 10% done to a designer.

All of the above, especially the latter one... IS SO TRUE.