It is AWESOME. I have been seeing the 1 hour 20 minute video.... watch it too on the site
Google Wave - Communicate and collaborate in real time
They distributed 1,00,000 invites on 30th September and giving 5 to each new person if I am not wrong. If you have an invite already, please mail me one at p r a t y u s h k h a i t a n @ g m a i l . c o m
Can't wait for it to be accessible to all and try it.