Basically in laymans terms most fuzz's particularly Ge ones are very sensative to the low impedance produced by active electronics, this generally results in a very quished or gated sound from the fuzz, the fuzz can't get very loud and it has that almost synth like attack to it.
The impedance buffer changes the impedance of the tone to that which is ideal for a fuzz somewhere between 5,000 and 12,000 ohms or even up to 25,000 in the case of this unit (Impedance will be variable). This can be different from a passive bass to but it is the ideal driving force for a fuzz pedal, this results int he fuzz working properly with all basses, anywhere in your chain and isn't effected by other pedals such as Boss being in front of it as again those pedals have low impedance output and buffered bypasses and such which will as stated above affect a fuzz pedal.
I'm not into whether people want these or not, I've had one built for me in a blender pedal and it works like a charm there is no difference in tone with it on or off and the fuzz pedals work great. I have many pedal building friends and 2 have offered to do this for me, one to design and build a prototype and the other to mass produce and sell it if needs be and also package it in a small nicely painted box as a standalone unit instead of being in a blender. I have offered it around here, not because I will make any money on it as I won't and don't care I know quite a few players that want/need them and I myself want a few for various live and studio work I do.
Hope this helps