Communication & Collaboration - that is what email is all about - or should be. The GoogleWave concept mimics the snail-mail and a wiki at the same time, while being a protocol and an application also. The demo looks like a cooperative instant-message chat, but showing character by character, making an almost f2f chat impression... Who used OneNote online before, may be used to see the joint changes of multiple participants in one document - but it is amazing to see even uploads of photos and other material into the wave in a blink of a eye. To see somebody adding a Google-map into the wave and have it adjusted to show the right location IS amazing!
Let us put it like this: As a digital nomad and "never in the own office" worker, I want this, and I want it NOW! Now for Enterprise 2.0: adding a SAP Business Process Design tool Gravity to Wave enables cooperative work on new process designs inside the Wave. Re-designing processes to adjust changes caused i.e. by Mergers & Acquisitions now becomes easier due to real-time collaboration between subject matter experts. Cool user experience...