In general they only work well in clear water. I have used them down to 30 ft for perch when I used to lug the original aqua view around. I would never put it in the same hole I was fishing out of though. I always drilled a separate hole about 4 to 5 ft away for the camera and would get it positioned so I could see my lure. You can learn a lot from it, especially how many bites you get that you never see on your spring, in line movement or feel in the rod. It can be very frustrating to see all the bites you 'miss'. It will also show the importance of not having a jig that is spinning in circles. Unless it is one of those days that rarely happens where they are biting like a kamikazes, the fish will often just stare at a spinning jig until it stops. In line reels help with line twist and so does changing the line you are using often.
I would take a finder over a camera any day of the week, but the newer pocket sized mini cameras still can be useful to see what is down there and are easy to deploy and store easily.