Answering my own question. HTH
Found the following in the VMMSSPV2Install.log in my user docs dir:
ConfigureIIs: failed to get IID_IMSAdminBase Object
Error 26001. Cannot connect to Internet Information Server. (-2147221164 )
MSI (s) (B4!F0) [14:55:34:257]: Product: System Center Virtual Machine Manager Self Service Portal 2.0 -- Error 26001. Cannot connect to Internet Information Server. (-2147221164
I was missing "IIS 6 Metabase Compatibility" as a part of my IIS install.