If you have been thinking about getting Kinect, this is a fantastic deal!
I found out from Gamespot that Microsoft® has officially announced a new "while supplies last" bundle with the new Xbox 360 console and Kinect! You get both the console ($300 value) and Kinect ($150 value) for $399. This bundle will apparently be released November 4, just 6 days before Kinect is released! I foresee these going really quickly.
If you want want all the extra hard drive space a 250GB console will get you, you can get the same bundle with the new 4GB console for $299. This is available now through a lot of retailers like Gamestop, Best Buy, Newegg, and Walmart.
Note: I haven't seen an official press release for this new bundle yet, but if I do, I'll link to it!