I had used wave pretty heavily too. For one thing it was a way to chat through the company firewall when i was still doing a 9-5 ;) (they hadn't block it) though more importantly it was a great way to jot down ideas back and forth during the day , comment on the add some images then tabulate them or add them into bug tracking/feature control system at the end of the week.

Sometimes the ideas would evolve on wave after a week and we would put the final result in our bug tracking/feature control system with a reference to the wave so we can remember our rational behind why we added or changed a feature.