I mean the sloshing paint at a wall versus signing your name alone should tell you everything you need to know. Maybe I just find engineers endearing but those actual game play demos were far more impressive as a proof of concept than the seemingly pointless, and ultimately faked Milo demo.
There was a really nice reaction to the writing from the audience. details like that impress those that dream of what they or others can do with that precision for gameplay.
I think part of Wii's success and part of Natal's hype is the inaccuracy. the average person isn't good at stuff, and if you give them something accurate enough to show their faults up they wont like it.