Like larry, I have a Char Broil elec. water smoker. I liked it out of the box, once I fixed the loose socket for the controller.
I had considered adding lava rocks for retaining heat. I read about the heat retaining properties of sand in the pan instead of water, tried it, and love it. A good rub on the meat helped seal in moisture/juices, and I didn't have to fiddle with adding water, etc.
I have used extra lava rocks in a two burner gas grill smoking situation (with one burner off under the meat, of course). It helped with the 'thermal mass' quite a bit, so much so that I could cycle the burner on and off every 30 minutes.