Since you are working on your swing and the club is hitting through the ball as opposed to you hitting at a ball, it would be better than nothing when practicing your full swing. It beats breaking a neighbor's window or knocking out one of the neighbor's kids.
I hit them at home when I can't go to the range. I don't recommend chipping with them, you don't get the feel of hitting a real ball. I practice chipping at home with real golf balls.
I prefer hitting the real thing.