Initial setup:

By default, the pipette-key is set to the 1/2 key on a swedish keyboard, but internally Blender registers that as a backslash. 

If this doesn't work with your keyboard language layout I've added the possibility to remap the Pipette key to a key of your liking in the preference > keymap.

How to use:

The way Material pipette works is that you press and hold the "pipette"-key then sample a Shader with the left mouse button and paste it with the right mouse button.

If you at the same time as you are holding the "pipette"- key, press and hold the shift key and sample a Shader, you sample all the material slots on that object.

If you at the same time as you are holding the "pipette"- key, press and hold the shift key and paste a Shader onto an object, you replace all instances of the old Shader with the one you sampled.