Had experience of PDR in the UK, the results were excellent. As to increasing metal fatigue, no. The metal is just being massaged back to its previous form.

 

I had a small dent from a shopping cart fixed on a side door, and DentWizzard did a great job. From what I understand, they took the door apart and used high powered magnets to pull the metal back out and smooth it. It is a black car, and if you look at it from the right angle under sunlight you can see "waves" in the metal, but running your hand over it you can't feel anything.

The whole thing cost something like US$190.