Regarding whether Kinect is playable: according to Major Nelson they have a Kinect speficic area, here was a pic of the line to get in (from Major Nelson's blog); http://twitpic.com/1xbwdv
On topic I'm not sure I'm as keen on Microsoft's press conference this year as the op. In my opinion it was not as powerful or successful as 2008 or 2009, but that doesn't mean I think it was bad.
It's also a long road till Microsoft is competing with Nintendo sales wise I think. We'll have to see the pricing on Kinect and how the software offerings resonate with consumers. Nintendo has been able to stay ahead of thier game because the promise of the Wii-mote has been realized by some great games, and they have supported thier hardcore with traditional offerings. It's a fine line to walk, we'll know in the coming years if Microsoft has the skill to walk it.