Well Microsoft got this out pretty quick, considering they just acquired the Giant Software about 2 weeks ago the maker of the AntiSpyware. For details on the recent acquisition read the InformationWeek article.
You can download the beta version of MS AntiSpyware here:
http://www.microsoft.com/downloads/details.aspx?FamilyID=321cd7a2-6a57-4c57-a8bd-dbf62eda9671&DisplayLang=en