After having switched to KDE from Gnome, I can say Gnome Shell does hurt productivity. One example would be, Nautilus can't be split into two panes. When I have to move a bunch of files from one folder to another, on Gnome it would require right-click copy and then open the folder and then right-click-paste. Whereas on KDE, it merely means drag and drop. It will even ask you, if you want to move or copy, that could come handy at times. Usually, I have a working folder open in split and a new tab if I want a full folder.
Secondly, KDE comes with a full suite of applications [1] that all follow same philosophy of user choice than minimalism. Gnome severely lacks that kind of application database. For example, there are not many applications, including big names like Banshee, that use Gnome's message tray. Some applications use split menu and some don't. Overall, it's not a great user experience. Not to mention there is no way in Gnome to entertain Dropbox icon which is specifically designed for system tray.
[1] http://www.kde.org/applications/