Have been watching the I/O 2009 Google Wave Dev demo at http://wave.google.com. Looks really cool but so far I am not sure how stable it will be with tons of users. With real time updating character by character.
Personally I would love to see this working with 10K users like some old school forums I used to visit and post on. I would see this slowing way down or being so crazy it would be come unusable.
Still it is exciting to see tech like this for HTML 5 and I hope stuff like this get the IE team realizing that it needs to conform to Web Standards to make the web a happy place for all. Check out the demo if you have time and let me know what you think via twitter or plain old email.