UI is essential for most Apps. At jEyLaBs we spend a lot of time and energy on re-imagining UI for our clients. Recently we delivered 3 process applications on K2/SharePoint. We took paper forms and delivered applications that changed the way they work for the better.
A good part of this project was spent on working with the user groups understanding how the UI is presented to them, how user interactions and validations will be working hand in hand, how the business rules are presented to them in a meaningful way and so on.