So I finally tried Wave - So Paul Buchheit finally tried Google Wave und macht ein paar gute Überlegungen dazu.
From what I've seen, the realtime aspects of Wave are both the most intriguing, and the most problematic. I think the root of the issue is that conversations need to be mostly linear, or else they become incomprehensible. IM and chat work because there is a nice, linear back-and-forth among the participants. Wave puts the conversation into little Gmail-like boxes, but then makes them update in realtime. The result is that people end up responding (in realtime) to things on other parts of the page, and the chronological linkage and flow of the conversation is lost.