Yup, summed up much better than I could.

FWIW Joel's coverage of user design is a great read for things like this: http://www.joelonsoftware.com/uibook/fog0000000249.html

> Most flame wars you read about user interface issues focus on the wrong thing. Windows is better because it gives you more ways to resize the window. So what? That's missing the point. The point is, does the UI respond to the user in the way in which the user expected it to respond?

Most open source tools tend to be written by developers for developers and very rarely take into account the usage patterns of users in the domain which the tool fits. Want to know why Slack is tearing into all these areas that IRC could never get a foothold? You have the answer right there.