Hi, yes we have an issue with Salesforce whose policy is strict; IDP Initiated fails with Salesforce and we can see in their SAML validator tool the error :

Last recorded SAML login failure: 2015-04-09T05:55:01.385Z
Unexpected Exceptions
Ok
1. Validating the Status
Ok
2. Looking for an Authentication Statement
Ok
3. Looking for a Conditions statement
Ok
4. Checking that the timestamps in the assertion are valid
Ok
5. Checking that the Attribute namespace matches, if provided
Ok
6. Miscellaneous format confirmations
InResponseTo must be empty for Idp-init Browser POST Profile

regards