It appears that the ACS has IDP-style features within the "Service Identities" section. How does the ACS treat these in comparison to a real IDP? What is missing? Some examples I'm thinking of ...
I'm configuring my relying party (a website) to use either ADFS or Azure ACS 2.0. ADFS 2.0 has some interesting features such as Token Replay prevention (in the SQL version) and may have other SAML ...