This worked for me. I just left the directory path at the default and no issues. The first go around, I changed the installation path to D:\, and even with 8dot3names enabled, it still failed with the same error. Also, I followed VMware's documentation to a tee as far as installation. I ran the RSA scripts instead of manually creating an SSO SQL account with dbo permissions, etc. There seems to be two ways to go about installing SSO; either use the scripts and don't change the default path or manually create a dedicated SSO account and let the install runtime execute the scripts to create the RSA accounts. Either way, the install process definitely should be more streamlined than it is today. Also, I always install all components separately instead of opting for the 'Simple Install' method. The implementation seems to be sensitive to the order of installing the components, so I install manually and follow the order: 1. SSO, 2. Web Client, 3. Inventory Service, 4. vCenter.
Hopefully, this provides some assistance to those running into issues.