I've seen this comment made several times, mostly from you---where are you guys getting this from?
I think you are getting confused by the terminology. Molyneaux mentioned he let a developer 'drive' Milo...that's what Claire was. There was no man behind the curtain, all he meant was Claire knew how Milo behaved and knew how to 'trigger' certain events for him to respond.
We've seen plenty of demos, including impressions from people who have used it, of a retail 360 running a fast-paced and demanding game with Natal without any performance hit. So yes, we've seen it. But let's please stop with the accusations that Milo was a puppetshow, it's absolute nonsense. There are legitimate complaints and concerns about Natal, you'd best be served by focusing on those.
I'm getting it from ListenUp and Giant Bomb Cast, folks who went to see "Milo" live in action, and said that a developer was hooked up to an Xbox 360 via Laptop doing "something" to trigger reactions from Milo. I dont' recall which podcast, but one of the members said Milo failed to response, and then conveniently reacted when the developer was paying attention again. It's extremely "suspect".
Even then, Milo isn't that impressive if he only reacts to certain trigger words. Voice recognition is capable of pretty much the same results.
In reference to the other demos, again, we've seen nothing that requires very specific input. Everything is just general tracking of limbs. Even burnout, it's just tracking your fists moving.
I think it's more legitimate to question the technology than it is to blindly accept it for the charade that it was presented as.