Take the time to explore, to test your work, to learn and iterate, then test again. Take the time to learn more about who will use the product of your work, about their goals, desires, frustrations and obstacles. It takes time to learn how to do this well, to execute the work and incorporate it into the rhythm and governance of the project. But in the end, a careful design process will eliminate at least some of the 60% of functionality that is rarely or never used, and therefore wasted effort. Good design practices will yield more useful, usable, emotionally engaging and coherent experiences and create business value.
Consider optimizing for business, user and customer impact and effectiveness. Beyond scope, schedule or budget, we believe this is the way to measure IT.