I agree with most posters here. It doesn't work well if you have a weak server or a good returner. The idea is to confuse the other players and perhaps take away the shots they like to go for most. I think it's only effective for pretty good/fast volleyers.
If it isn't executed well I feel like DTL winners are easier than normal. For example, in a mixed doubles match the guy was serving to me on the ad side and went down the middle. I returned it to the deuce corner for an outright winner. They did it 3 times in a row against me and I hit the same FH winner in the same spot every time! I knew the lady wasn't quick enough to cover DTL from an I formation, so in my mind it was easier for me to hit the winner than if they did the normal formation.