Microsoft Ops posted an interesting blog about "the top 10 changes that we encountered in IIS7.0":
http://blogs.technet.com/mscom/archive/2007/09/07/the-tasty-morsels-found-in-dogfood-mscom-ops-top-10-changes-in-iis7-0.aspx
ORCS Web has also been running IIS7 in production on a number of sites for the past year or so. It is a very exciting product and we are looking forward to the RTM when it will become our key deployed platform.
~Brad