One of the things I like best about the current state of UI libraries like Ext JS or Flex is that they allow for prototype driven analysis.
As user story definition replaces traditional use cases, competent user interface designers can BEGIN analysis discussions with functional prototypes.
In traditional paper wireframing approaches, user's tend to hesitate until they can see something concrete.
Having users interact during analysis allows for a fuller undestanding of how the system workd that paper just can't provide.
The development benefit is the production of integration ready analysis assets. As UI widget libraries and pattern libraries continue to grow, the lag time in the discover-design-review process will also continue to decline. Ext JS, for example, continues to extend the combinations and permutations of data display grids, adding the concepts of grouping rows, expanding rows, and so to provide designers with a highly visual interactive palette with which to driven focused, effective system design meetings with customers.
