My generous chum
Max, recently sent me an invite for google wave. So far it's not terribly interesting since I have no invites to send to others. It suffers from the
Metcalfe network effect. Gmail didn't have that issue, since it was instantly useful and compatible with existing 1960s technology.
However, I am currently participating in a wave for my friend Lila, where I share accumulated knowledge, to help her and Brendan upgrade their ancient PC hardware to something cheap but modern. For this particular task, Wave is proving quite useful, like a weird little notebook, where I can attach footnotes randomly to any word and write the document in an asynchronous stream of consciousness. I guess that's the future of Email :)