Thanks to a generous soul at work who sent me an invite I am now using the early build of Google Wave. First impressions? Well, I can see how good this would be straight away, but it immediately hits you that you can't communicate with the people you want to because they are not using Wave.
I realise its early days but maybe some simple integration with standard email would be a good idea, where if someone wasn't using wave, an entry would be emailed to them, and their replies would appear in the wave.
Still, its shiny and new, and very interesting stuff. Time will tell I suppose.