I wouldn't want to put this on my acoustic bass, but it sounds GREAT on my EUB. It is a very simple design, and a very effective design. The ability to adjust the pole pieces for string-to-string balance is key. It can hum some depending on the situation, but the hum issue is far from outrageous - the pickup is best used in situations where that doesn't really matter anyway. I have mine mounted on an EUB in a customized setup with the option to run the passive pickup signal directly to an amp, OR through the Fishman Platinum Pro-EQ outboard pre-amp/DI that I have attached to the EUB. It works great either way.
It sounds best to me on its own, not even blended it with a piezo. It's really nice not having to deal with that piezo thump. (I have a Fishman Full Circle on my doghouse that I love, but I've struggled with other piezos on my EUB). I use orchestral strings to limit the sustain, but it's really only an issue at higher volume levels where if I used my acoustic bass, sustain would be excessive AND feedback would be a problem. I do set the string height up for a more blunt note shape, and it works really well.
This is a great design, and I'm very happy with it. I'm sure something like a Biesele would be awesome, but the Schaller is a nice product too, when you embrace it for what it is - a reliable, feedback-proof device to give you useable and easily EQ'd bass tone in ANY setting. It is not advertised as "your bass, only louder," but it could be advertised as "your strings, only louder, and with no feedback or piezo thump."
It's a good magnetic pickup.