You might also want to use KDE for Windows to explore KDE software still in development. For instance, running the latest version of KOffice on Windows is almost certainly easier for the average user than building it from source using CMake. The same is true of the DigiKam camera program.
Another use for KDE on Windows is to compare free utilities with Windows' proprietary ones. In most comparisons I made -- Dolphin with Windows Explorer, Konqueror with Internet Explorer, Kate with Notepad -- the KDE app was more configurable and included more features than their Windows counterparts. Admittedly, the KDE utilities are more familiar to me, and I prefer their free licenses, but seeing the two sets of utilities side by side was a strong confirmation of what I've always suspected.
With KOffice and MS Office, the comparison was not so one-sided. Even in its second version, KOffice is not as fully-featured as MS Office. But then, it has never claimed to be, and most people should find it enough for everyday purposes.
But KDE on Windows is more than a showcase of programs. If you choose, you can also run C:/Program Files/kde/bin/plasma to run the KDE 4 desktop, and run the KDE desktop instead of the Windows one. Only the task bar will remain of the original desktop, and you can press Ctrl+Alt+Delete and select explorer.exe from the Processes tab in the Windows Task Manager to rid yourself of that. You can even set the KDE desktop to run as the default desktop.
However, such steps do have the disadvantage of leaving you without a terminal. If you want to run any Windows applications, you will either have to set up a Folder View with the necessary icons, or else navigate to the executables with the file manager.
Still, the idea of shoring up Windows by running a FOSS desktop on it is an appealing one, and worth trying at least once. It may also be the surest solution available for all the annoying notifications that seem impossible to remove permanently from modern Windows desktops, regardless of how you edit the registry. Moreover, like the KDE applications, the KDE 4.2 desktop is more configurable than its Windows equivalent.
As a novelty, KDE on Windows is first-rate -- or should be, when it reaches its first stable release. I can understand, too, its appeal as an engineering feat for the developers.
All the same, a question kept occurring to me: Is there any point to such ingenuity?
Most Windows users will probably never hear of it. Of those that do, only those who are dissatisfied with Windows will try it -- and if theyre looking for alternatives, wouldn't they be more likely to try a GNU/Linux distribution than an alternative that still depends on Windows?
The only niche market I can imagine is members of the FOSS community who use Windows as part of their employment. For such people, KDE on Windows offers a familiar environment, with more customization and better performance than Windows itself. If you have to use Windows, then an alternative like KDE on Windows is definitely the route to follow. Even GNOME users are likely to prefer working in KDE to unmodified Windows.
For many of us, I suspect that KDE on Windows is something that we will try for a brief afternoon before scuttling back to GNU/Linux. But, if you have to use Windows, then maybe KDE on Windows will soon be able to relieve much of your pain.