I actually used it -- and liked it. For limited uses, but it was pretty cool.
My family and I have been using it to plan and talk about their upcoming visit, and it was nice because it kept the discussion sorta organized. We'd previously done such chatting in a shared document, but the wave was nice because it showed new comments that were inserted into the main text, so if somebody had a new thought about something early in the wave, they didn't have to put a date stamp on it (which is how we used the document sharing feature before wave came along).
It also had the advantage over chat because we didn't all have to be in the wave at the same time -- and considering the distance between us, and our work schedules, etc., required a huge amount of coordination.
I'm gonna miss it. But fortunately, they won't take it away until after their upcoming visit, so we'll still be able to use it until then!