I have been through several different upright pickups (Fishman, Underwood, and a couple other piezo setups). The String Charger has been the most dependable and least feedback prone of anything I've seen. With their add-on piezo setup the tone is quite good for everything but arco style.
Signal is a little weak, but a SansAmp pre-amp more than takes care of that.
Only system that I have seen that I liked better was the
Barbera setup but it is much more expensive.