You want to hire people who are always thinking critically about the ease of a user interface, even outside of work. In my freelance work I am using a marketing program called TXT-180. For a long time I had been annoyed by the sequence of options offered in the pull down menu for scheduling how frequently a message should be sent. It always seemed like "Once" should come before "Daily" (if thinking hierarchically). But the pull down menu did not have it that way. I was going to put a screen grab of this problem here, with a comment about how I would have done it differently. And I contemplated sending a letter to the people at TXT-180 with a suggestion to change it, when suddenly, they announced a new and improved interface design... which included the re-arrangement of "Once" at the top of the pull down list!!

I think critically and with the user in mind, and that makes me notice things! You want to hire people who pay attention and notice small but important details.

Hire for character, train for skills.