I already have few post about active guitar wirings with on-board buffers, but I didn't wrote an article, about reasons of building that stuff and it's benefits. So, here it is.
Some people, who mounted an active wiring with an on-board buffer or a preamp, or have active pickups in their guitars, are saying that this stuff changing the tone dramatically and it's a little bit too bright or less full, smooth sounding. I think, that it comes from some kind of misunderstanding the way how this electronics works.
If you mounted an active wiring, with a completely linear frequency response (for example audio op-amp based), the tone should be much brighter. It's because of transporting a full frequency range. Passive guitar wirings usually cutting off a little bit of treble. Active wirings are usually - like I said before - linear. They will just transport a guitar pickup signal. Thy will not cut anything if you don't want it. It's because of preamp or buffer impedance – high on input, low on output – and characteristic of working with the signal.