I was at Cabela's last week and asked about them. The sales associate mentioned that while they do work, they do not make murky water clear. Very obvious statement but it is something to think about if you are considering buying one. It would be pointless for me because the lake that I fish is not that clear. He said that it pretty much doubles the vision that you could see from the surface. For example, if you can see 2 feet down, the camera will be able to see about 4 feet in the water.
When in doubt, set the hook.