Although I haven't used KDE in a while, I applaud their efforts to make KDE apps available on Windows. Having lots of users is one of the most important aspects of a successful open source project, and the KDE developers have just opened themselves up to the remaining 90% of the user base.
The more you can get Windows users to use open source software on Windows, the less barriers they'll if/when they ever switch to another desktop OS.
My initial guess is that amarok for windows will be the most popular. I'd also be interested to see if they could produce a better Webkit-based browser than Safari for Windows.