SWDs are awfully hard on the young birds. Personally, we use them ourselves. They are usually good for at least one or two extra birds. The big marshes we hunt in... we use the remote control. Birds see it at a distance, turn and come passed to see the deeks... we cut it off, they work the spread, cup and drop... and we usually empty the guns in vain.
That said though, the very first hunt I used my particular mojo was the day before christmas of 2003, and the second duck of the day tried to land on it... that bird had a band on it that was 11 years old, and the bird had been banded as an adult. Maybe he never got the memo.
In my eyes its just another tool. I've heard arguements that its no different than hunting an impoundment or flooded field, its just a way to attract birds. I don't buy it. If you have a flooded food source, and if you shoot your limit and get out, you basically have created a semi-refuge. It sucks if you are trying to hunt around it because its hard to kill ducks that way, but in the greater scheme of things a flooded field that is not over hunted does far away more good for the birds than it not being there. A SWD doesn't help anyone but the hunters behind it, and thats only about a 50/50 these days.