Considering they come with a inexpensive uke, they are more than adequate. I've used a Kala Koa Tenor ukulele many times plugged into an amp, it actually sounds better than some custom ukes with a passive undersaddle pick up. The Kala pick ups are active, and use a camera battery that slides out from the outside panel with tone and volume control. I've had to use external preamps ($150) with tone controls to get the same sound of the much more expensive uke's compared to the Kala. The Kala doesn't sound as good acoustically, but once plugged in, they gig the big boys a run for the money.
You can't compare it with a Fishman prefix pro ($350) which I had factory installed on my Mele Tenor cutaway, but the pick up cost more than the entire Kala Ukulele with case.