Wesley S, your question piqued my curiosity -- looked around a bit, it appears that piezo is the only game around for mandolin-ish instruments. There are newer and better sounding technologies available for guitar and fiddle but noone seems to be making mandolin pickups with them.

If it's any consolation the worst case examples in this thread seem to describe poor installations as much as the characteristic piezo sound. A good installation, coupled with some judicious EQ can work pretty well, and of course you can always mic it for the best acoustic sound. Given the choice between a well-installed piezo and no pickup at all, I'd take the piezo, the convenience factor is really compelling even if the sound is less than optimal.