“Summary:

Agile methods aim to overcome usability barriers in traditional development, but pose new threats to user experience quality. By modifying Agile approaches, however, many companies have realized the benefits without the pain”

Long story short: Agility without usability is bad.

“Agile’s biggest threat to system quality stems from the fact that it’s a method proposed by programmers and mainly addresses the implementation side of system development. As a result, it often overlooks interaction design and usability, which are left to happen as a side effect of the coding. This, of course, contradicts all experience of the last 30 years, in which user experience’s importance in system development has steadily increased as we moved from mainframes to PCs to the Web. As the user base and the use cases have expanded, the need for top-notch usability has grown.”

Very exciting for designers. He advocates the use of paper prototypes to keep the flow of the user’s expereince cohesive in the face of one feature at a time development.

Nielsen also recommends pre-planned weekly usbaility tests.

Read it from the horse’s mouth.