I just had the best brainwave just now. You know when you have so many windows open at once and you want to navigate them quickly with just the keyboard? Normally you would hit alt+tab, look through the list for the window you want, then repeatedly hit tab until you reached the window. If you're a massive multitasker like me this can take a good 5-10 seconds to actually get to the window (Plus maybe a few incorrect window selections as well). So instead using the normal window switcher I set the "toggle present windows" shortcut to alt+tab.
Now, actually manually setting this shortcut to alt+tab instead of just changing the "window switcher" to present windows in the KWin desktop effect general tab entirely changes how it works. If you just change the window switcher to present windows it will display all the windows in a grid and highlight the one you will be selecting once you release the alt key, manually setting it means you can release the alt key and actually type in the name of the window you want to select by taking advantage of the present windows window filter. Isn't that such a time saver and a great use of desktop effects?
You can find the present windows shortcut either in System Settings -> Keyboard & Mouse -> Global Keyboard Shortcuts -> KWin or in System Settings -> Desktop -> All Effects -> Present Windows.
Now if only hitting the shortcut again will deactivate the effect... At least by hitting enter it will select your previous window by default.