Nobody reacted on my email to the devel mailing list, so I suspect that noone has any objections to my patches.

Anyway, this is what happens:
* I replaced the zoom combobox in the toolbar with the fit to width/page buttons. For one they look much cleaner and also most users would never use the freezooming anyway.
* Removed the frame from the sidebar, making for a cleaner overall look. After all, nothing else has a frame.
* Let the statusbar stretch over the full width of the window. This again makes the app look cleaner.
* Used the same trick as in Gwenview: let the background shine through -> clean++
* Use QToolButton instead of QPushButton for the minibar buttons to fit the other buttons in all apps.