One of the hallmarks of disruptive technologies is that they eat their way up through the chain of capabilities over time. With the rise of Ajax, DHTML techniques like drag'n'drop are becoming a lot more useful. And together, they're taking the web application up another step on that chain of capabilities. The gab to mimicking the rich desktop applications is growing ever more narrow.
Point in case: We just introduced drag'n'drop for reordering of list items and notes in Backpack. It freaking rocks. Yes, everything old is new again. But that's the point. OmniOutliner still has a much richer environment for manipulating lists, but I already valued the sharing and accessibility of the content more. Taking one step closer to the rich feel is going to do the same of a lot more people.
So we're getting closer every day. With the impending, upcoming release of Rails we'll include all this stuff right in the box. Rails is going to push the frontier of integration once again. Everything needed to build web applications like Backpack. Slick effects, cool interaction, and a solid MVC stack without having to strap on the professor hat.