I have grown to dislike saddle pickups of all kinds. The only one I found acceptable was a Baggs in my Godin semi-acoustic electric fretless bass which was always heavily preamped. The combination of factors like fretless/bass/semi-acoustic/etc made it a very different animal than normal acoustic guitar applications.

The installation (look for frets.com for installation tips) is critical. A clean and flat saddle slot, saddle bottom profile, and an absolutely unmarred transducer are a good start. Nonetheless, without a preamp, preferrably a very good one, a saddle pickup will sound lousy to my ears.

The only place I like piezos of any kind are when they're mounted against the soundboard. I currently own two guitars equiped this way, but each are dual piezos and they're really intended to be used as a "threshold" (minimum) signal source and/or in conjunction with a mic or soundhole pickup.

Don (above) is correct, the preamp issue is paramount. I generally like to use a preamp on every guitar signal regardless of its source. Sending that signal via a direct box to a board with good mic preamps is also vital. You don't need a direct box and preamp dedicated to each guitar if you use an A/B box or other switching mechanism.

Mooh.