I've been using a Baggs M1A in my GA3 since I got it. Sounded decent, if slightly electric (a common complaint about soundhole pickups). Since a had an MiSi Acoustic Trio laying around, I decided to give it a try. This pickup used the Baggs Element UST connected to a preamp that runs off a large capacitor, i.e., it has no battery. You charge the cap with the supplied adapter and it's supposedly good for 8 hours of playing time. Have never tested that but the charge does last for several days playing 30-60 minutes a day.
Anyhow, it also sounds decent and a little more acoustic sounding than the M1A. The UST quack is fairly subdued (which I've found to be the case with the Element) and certainly at a level I can live with. I had used this pickup in my Martin (which I sold) and will keep it in the GA3 until I find a reason to change. BTW, I am using it with a bone saddle but I can't tell the difference between bone and Tusq in this guitar. The bone was just a lot easier to sand down to compensate for the pickup thickness.