The Senior Development Director for C&C 3, known only as 'Smudge',
posted on the official forums with a few points of interest.
-- Anyone who has the full retail game installed will be upgraded to Participant level when you register the game. This will allow you to participate in BattleCasts (playing and commentating), as well as plan future matches through the online scheduling system, and participate in clan life.
-- If you have the game installed you will also be able to spectate live matches as well as watch archived BattleCast matches.
-- We will be making a free, downloadable BattleCast Viewer available, which will allow you to spectate live matches and watch archived replays. We haven't made any announcements about when the Viewer will be ready. It's not exactly imminent but I don't expect it to be too far out either. Is that vague enough for you?
-- The game has already shipped out to a few retail stores in Europe. The game ships out today to stores nationwide and will be available for purchase everywhere on Wednesday.
'Participant' is just a level on the forums, I believe. We'll see how this BattleCast thing shakes out, and if many mainstream players use it. Ultimately, I think that will be the best way to judge its success.
