If I pay for the enhanced version of StarDock's WindowBlinds, besides the features listed on the Buy page, is there anything that a single user would need from the Object Desktop pack?
Object Desktop is simply a compilation of most of Stardock's desktop products. It includes Windows Blinds. This option on the buy page is an advertisement for the compilation, not an actual "other license" to Windows Blinds.
If you want to buy only Windows Blinds, you want the "enhanced" edition. If you are interested in more products (like Icon Packager, Fences Pro, etc.), you can consider buying Object Desktop.