I have used a Woodpicker® on a Greek baglama (i.e. "octave-bouzouki") and, for the price (+/- $35) it's OK. It sticks (non-permanently) on the soundboard.
I have heard arguments against it from several folks whose opinion I respect: Namely, that it "has no bass response"; probably true, although it has not bothered me, considering that the instrument only goes as low as D, i.e. the mandolin's second-from-the-top course.
MY own, very real complaint is how feeble the wire connection is. My initial pickup went dead after a few weeks of use; I returned it to the manufacturer, who duly replaced it —very good service. Now, the replacement is having "hiccups", too; a nuisance...
But, for the price, it works. For when I upgrade, though, I am eager to hear what others think about higher-end solutions.
It is not man who lives, but his work. (Ioannis Kapodistrias)