The changeover appears to have started around the 8th January, when www.microsoft.com began responding sometimes with
Microsoft-IIS/7.5, but with many requests still being served by 7.0. Now the transition appears to be complete, with all requests now being handled by version 7.5.
Microsoft has consistently upgraded www.microsoft.com to new versions of its web server platform ahead of their actual release, as a demonstration of confidence in new versions. It upgraded to the original Windows Server 2008 in June 2007, 8 months before that operating system's finished release in February 2008. www.microsoft.com is one of the very first sites to use Microsoft-IIS/7.5; Netcraft sees only 28 websites running Microsoft-IIS/7.5 in the February web server survey, of which the only significant sites were at Microsoft.
The major changes in Microsoft-IIS/7.5 are mainly new features that were previously available as separate add-ons to IIS 7.0. These include a new FTP server that integrates better with the web-serving side of IIS, which aims to make content publishing easier; similarly a new webdav implementation; and the integration of the IIS7 Administration Pack and Powershell. There are some improvements to existing features, including improvements to FastCGI support. A best practice analyser (BPA) is also included, which should highlight instances of poor configuration.