If you guys have ever worked on a newer car, you will soon see the need for an easily sand-able filler. On the Honda above, I just finished filling a small dent in the right rear fender. The metal was so thin that it kept popping in when I tried to sand it smooth. Sanding a two part filler perfectly smooth in this area of the car was impossible. I was glad to have the putty.
Body putty works excellent for small dings and imperfections in the paint itself. I think that people have problems with shrinkage only because they don't allow the putty to fully cure.
Also, when it's 100º+ in TexAss, you only have seconds to mix and apply the two part filler. I guarantee that you will get some bubble, pinholes. Putty is perfect for filling them.
Ya'll worry to much.....