From the website:
Many technological innovations rely upon User Interface Design to elevate their technical complexity to a usable product. Technology alone may not win user acceptance and subsequent marketability. The User Experience, or how the user experiences the end product, is the key to acceptance. And that is where User Interface Design enters the design process. While product engineers focus on the technology, usability specialists focus on the user interface. For greatest efficiency and cost effectiveness, this working relationship should be maintained from the start of a project to its rollout.
When applied to computer software, User Interface Design is also known as Human-Computer Interaction or HCI. While people often think of Interface Design in terms of computers, it also refers to many products where the user interacts with controls or displays. Military aircraft, vehicles, airports, audio equipment, and computer peripherals, are a few products that extensively apply User Interface Design.
Optimized User Interface Design requires a systematic approach to the design process. But, to ensure optimum performance, Usability Testing is required. This empirical testing permits naïve users to provide data about what does work as anticipated and what does not work. Only after the resulting repairs are made can a product be deemed to have a user optimized interface.
The importance of good User Interface Design can be the difference between product acceptance and rejection in the marketplace. If end-users feel it is not easy to learn, not easy to use, or too cumbersome, an otherwise excellent product could fail. Good User Interface Design can make a product easy to understand and use, which results in greater user acceptance.
Caveat: I know nothing about this company or it services other than what I read on the website.
I am listing their site because of the wealth of materials they have gathered together on this important area for topic map authors.