I'm surprised no one has mentioned B-Band pickups yet, but perhaps they're not so well known in the States. They're a Finnish company and have been around for a while.
I was put onto them by Martin Seeliger of Lakewood Guitars, as he used to factory-install B-Band PUs on his guitars before he (co-)developed his own system. All my guitars (except my F50) are equipped with B-Band active pickups, several generations, in fact, and I have always liked their sound enough to continue using their products. Being a studio guy as well as a touring muso, I'm painfully aware of the fact that a transducer will never sound like a Neumann mic, so amplifying an acoustic guitar will always be a compromise between authentic tone reproduction and hassle-free amplification.
The B-Band system I use is the simplest of the bunch, the A1 preamp, which lives in the (replaced) strap button, along with an under-saddle element (UST), which is not a piezo, but some kind of condenser job. The UST is so thin, you needn't even shave your saddle down to regain your preferred string action. The latest generation of this system comes with a thumb-wheel volume control which is mounted inside the soundhole.
The B-Band system has an extremely high tolerance to feedback, although the size and resonance of the guitar play in important role in this respect - you can only blame your PU system to some degree.
For my F50, I have just purchased my first dual B-Band system, which I have yet to install. It combines a UST with a soundboard transducer (also a condenser element). The preamp is a little box that is mounted inside the guitar and feeds volume and balance thumb-wheel controls mounted in the soundhole. The guys at B-Band told me that soundboard transducers are inherently more feedback-prone than USTs, that's why a balance control comes in handy. Solo gigs - balance towards the SBT: very natural tone as the mids and treble are drawn from the SBT and only the bottom end comes from the UST. Band gigs with loud monitoring - balance towards the UST: slightly more metallic (but still pleasing) tone, as the UST provides most or all of the amplified sound.
While I still have to see (hear) how the combined system fares, I can't recommend B-Band highly enough. AND, the system I use is very affordable.
Cheers
Recky