I am in the Auto repair business, and I do paintless dent repair on occasion.
The quality of the finished product, depends on several factors.
The location and severity of the dents.
The color of the vehicle.
The eye of the owner.
Unless the dents can be removed to the point a light sanding, and buffing, will remove the final traces of the repair, there will be some sort of visible clue.
How visible depends on your eye. I have seen some that looked like a bag of frozen peas, painted the color of the car, and people thought it was perfect. :confused2:
Most of the time they can remove minor dents to the point you really don't notice them.
The technician doing the repair, will usually tell you what to expect. And, if your not happy with the results, you can always have the repair done conventionally.