Re: piezo pickups for electric guitars
I haven't tried those Fishman pickups, but I've had a Graphtech Ghostbridge, which was pretty cool, and worth looking into. Apparently LR Baggs makes some good ones, too.
With at least the Fishman one, I believe you get a choice between using passive electronics and using their preamp, but the concensus seems to be that they sound horrible without the preamp. With the Ghostbridge, the preamp integrates seamlessly with existing passive electronics (and I believe with actives, too, but it's more work). The documentation on the various website (I'm most familiar with the Graphtech one) seems pretty exhaustive, too, so you should find all the answers you need there... or email them - they're very helpful.