Feedback from user groups will flood creators with new ideas and changes to be made to a product. Creating mock-ups and early prototypes that are easy to edit are important to keep design fluid. A product must be malleable during its early stages and developers must consider user feedback seriously. There may be oversights and feedback from diverse sets of users will help combat this. Developers that are stubborn and make few changes and barely look for feedback will lose out on information from populations of users and the product's usability will suffer as a result.
Designers and engineers will very seldom "get it right" on the first iteration of the interface. Often the feedback from the users will help facilitate change greatly in any given product.
Courses
Feedback