Reworking a site to improve usability is often considered a big deal. Jesse James Garrett (the guy who coined the term AJAX, and considered a top user experience expert) adds an interesting perspective:
We tend to think of usability as the foundation of the work that we do. It sets the minimum requirement for a design to be successful, so if youâ€™re not doing usability work you wonâ€™t know what that requirement is. Philosophically, thatâ€™s where we come from.
I think a lot of people look at usability as the ultimate end goal of the design process, but we donâ€™t see it that way either. We see it as the place that you start, but there is lot more that a design should do than just attaining usability.
Usability doesnâ€™t really get at the psychological and emotional context of use. Usability will tell you, from an ergonomic perspective, what people can do with a product, but there is lot more to making a product successful in the marketplace and making a product feel successful in peopleâ€™s minds. Often, we find that clients come to us, thinking they have a usability problem, but it turns out that their products are pretty usable. The reason that the product is falling short is it is not satisfying an emotional or psychological need.
— Jesse James Garrett on Ajax, Amazon and Web 2.0, E-consultancy.com, August 2007