I enabled "Only one window per application" partially because I really liked the GNOME 3 way of doing task switching.

In KDE under "Only one window per application" much like in GNOME Alt+Tab switched between applications and Alt+` switched between windows within an application. The great thing about GNOME was that I could go between these two modes of task switching without exiting and re-entering the task switcher. 

In KDE I can't do that unfortunately. In KDE first I Alt+Tab my way over to the other application I need. However because I need a different window in that application than the one that was currently selected I was hoping that once I reached that application instead of Tabbing I could switch to `ing to select the specific window that I need. However I cannot switch from Tabbing to `ing. Once I reach the application that I need my only way of reaching the window I need within that application is to first completely let go of Alt exiting the task switcher and then to restart it in Alt+` window switching mode.

In GNOME this was not a problem. I could freely switch between Alt+Tab and Alt+` without having to restart the task switcher and could switch back and forth between these modes as many times as I felt like it. GNOME 3 style task switching really is about as sanely, quickly, and efficiently as task switching can be done. I hope KDE will also allow users to adapt such a style if they so wish.

Reproducible: Always