We can lose or gain users as a result of design changes. Terrifyingly, we can lose money due to bad UX design. So you can see how crucial it is to make the right UX decision.
At Revelry, we use BDD for all members of the team — and yes, that team includes our clients — so that everyone is clear about the intended user experience in the final product. Revelry’s flavor of BDD is a process for describing software features that is biased toward user’s actions and the results of those actions.