Huge mistake! I loved Wave, and used it very successfully on one creative project. When I tried again, with some of the same people, we'd collectively burned all of our invite tokens and couldn't get any more, so we had to revert to emailing things back and forth so the new folks weren't kept out of the loop. That killed it, as far as any of us were concerned. I think I used it one more time, to plan a party or something with my sister, and never again. Integrating it into Gmail, as you suggest, would have been a better path, but hardly necessary. It was great as a stand-alone product, but destroyed itself because the damn invite system stopped the network effect cold.