I've got an SSD that I use for the system drive and HDDs installed for data.
This setup worked fine with Win 7. I changed the registry values for Default, ProfilesDirectory, and Public to the location I wanted on the HDD and all was well.
This is not working for me in Win8. At first, I thought it was but then I noticed that right clicking on the lower left corner didn't bring up the context menu it's supposed to display. I tested this under multiple profiles and the only time it worked properly was when the profile was on the system drive.
Is there something more that I should know about putting user profiles on another drive with Windows 8? This may seem minor but that context menu has become important to me.