Sorry if this old hat, but stumbled across this interesting report
http://www.symantec.com/avcenter/ref...ackSurface.pdf
The report centres on the fact that MS have re-written the IP stack from the ground up. While this could be regarded as a good thing, there is a risk (as with all new and complex code) that new vulnerabilities may be introduced.
Do remember that it was the beta version that was tested, and some of the issues may be fixed in the initial rollout (although I wouldn't bet money on it!) but those using the beta may wish to bear some of the points raised in mind, particularly some of the firewall points, where the true stae of the firewall didn't appear to be consistently reported by different front ends.
The issues are reported to particularly affect home users. (Corporate users may (should!) have other/additional measures in place to proect their networks).