Yes, all my categories seemed to be nicely intact after installing 4.5. So far, so good. I did follow your suggestion, Mike, and exported my user data before installing the GenesisStarterEssentials. However, after completing the content installation and reopening D|S, I had to manually re-import the User Data as that dialog box did not automatically appear.
A lot of my old categorized content had yellow triangles with exclamation marks but they disappeared after I re-categorized the new content and/or removed the orphaned references.
Thanks to everyone for helping me installing D|S 4.5!