Since we have multiple vCenters I am currently trying to integrate vCO 5.5 with a vCenter 5.1 installation where the SSO service also is at 5.1.
So far this has led nowhere and I am starting to suspect that I really do need to run SSO 5.5 in front of every vCenter I want to share credentials with. But it would be nice with a confirmation, and I was not able to find this specific requirement in the installation guide.