Right now, I think Wave is more a toy than a full tool. Part of that is its feature set isn't complete and part is that we're all treating it like a toy. What I think Wave is ultimately going to become is a unified interface for Web 2.0. If they manage to integrate the service into social networks and blogs and forums and so on, we'll have one interface for the majority of online contribution and collaboration. Sure it's advertised as the next iteration of email, but I think its greater contribution will be to standardize the interface through which the majority of people interact with the web.
Google Wave has been fairly successful in organizing the Other Future of News (OFON) conference. Julio Ojeda-Zapata provides some details at the Pi Press site.
http://blogs.twincities.com/yourtechweblog/2009/12/local-media-writer-harnesses-google-wave-for-planning.html