I used to use one on an acoustic when I played live in a duo group. Some twenty five years or so ago. Looks very similar to the sound hole pups in the picture but had no pole pieces in it.
At the time there weren't to many pick ups on the market for acoustic. That's why I purchased it. As for sound, it was a little to electric sounding to my mind. So we used it in conjunction with a mic and blended the signals. Eventually got some good tones that way, but still not great.
Have no clue about the newer ones. I'm sure they've gotten better over the years though. I know when I start looking for a new one I'll be looking at the Sunrise sound hole pups and then blending that with a mic. They sound really nice after hearing it a few times.