On the whole is seems that the MSN search engine is indeed placing IIS hosted sites higher in the results more frequently than other web servers. Frequently the MSN search is placing more IIS servers in the important top 10 results than Google even where result sets from a query have actually returned fewer IIS servers overall on MSN.The full study can be found here
Looking at the coverage graphs, most search phrases return a more even spread of IIS servers throughout the results sets from the MSN searchs.
MSN Search favoring ISS?

Ivor Hewitt was a bit conspicuous that he got so many ISS powered websites when searching MSN's new search engine so he decided to start a little investigation to compare the share of ISS against other web server software on MSN Search and Google: