Installed this to a 2005 American Deluxe V Fender Jazz bass (together with replacing the onboard pre-amp with a 3 band Glockenklang) and the bass really improved:
-noise decreased,
-no more fiddling with the amp (whatever amp at rehearsal studios), just set them more or less flat and control the tone from the pre-amp
-stronger output signal (in passive mode), drives an envelope filter better.
Sound is very clear, rich and powerful.
Together with the pre-amp, this has been the best investment into my bass gear for a long time. Unfortunately I cannot tell, which one contributed more, but the overall result is perfect.
CONS: None at all.