I agree. I liked it back in the day, and the fact that you could attach people to subtrees of a conversation was rather cool. IT also fixes infinitely-deep email chain problem very well.
It reminded me of usenet in that respect, easy to ignore subtrees you don't care about.
What surprised me was Wave is obviously best for business, where email chains CC'd to a load of people who don't care are the norm, yet they killed it only months after enabling it for Google Apps
