I considered other pickups before settling for the SH713. It's a great value pickup and reproduces the sound of my nylon string guitar very well.
Had to extend the cable to allow me to fit the pickup comfortably inside the guitar. I would recommend using thin double sided tape instead of the included adhesive as this helps the pickup in sensing the vibrations from the soundboard.
It is worth positioning the pickups outside the soundboard first, before sticking them in place inside. Spend some time finding the best position for each transducer and it will help give you the best possible results. I have one transducer on the treble side of the bridge plate, one in the very center (half way between the bridge and sound hole) for the middle frequencies, and one on the bass side of the bridge plate for low end harmonics. A preamp is probably the best way to boost the signal from the transducer, however I have no problems plugging straight into my amp (Marshall AS100D). I would advise a graphic EQ unit/pedal or similar to remove feedback, especially if fitted into a small guitar; feedback will occur with all transducers fitted internally but the SH713 is very sensitive to even slight harmonics.
Overall a great purchase for acoustic guitar, and probably any other acoustic instrument. Would highly recommend.