Our colleagues at ZDNet Australia just conducted a very interesting experiment. They took KDE 4 to the streets and told people it was Windows 7 and guess what? No one could tell the difference.
Here's the comical experiment from ZDNet Australia's Chris Duckett and Alex Serpo. Perhaps this could be another installment of Microsoft's new Mojave experiment.
The video is based off of this Windows 7-KDE 4 comparison.