There are other articles explaining the requirements for IIS on the central administration server (see linked articles below) however these don't mention the requirements for IIS on an Active Distribution Server, what are these?
IIS6 compatibility is always needed on IIS7 our install scripts still use the old-fashioned IIS6 methods of configuring virtual directories, etc so this is required on all servers running our software through IIS.
For a distribution server, WebDAV is a requirement. It is how we enumerate files on a HTTP share so must always be installed and enabled.
For WebDAV you will need most likely IWA as authentication method on IIS 7 (especially if on a AD domain), see Additional Information below.
In IIS7 (Introduced in Vista/2008) Microsoft introduced a new policy where anonymous access is no longer permitted for use with WebDAV. If running IIS7 you will have to configure authentication on WebDAV and instructions can be found on this site: http://learn.iis.net/page.aspx/350/installing-and-configuring-webdav-on-iis/