I do not have a strong opinion on body filler. If I were doing a top-dollar restoration, I may opt for a different method of straighting out the sheet metal, but for a driver I don’t really see much of a problem using the stuff. For starters, it doesn’t seem all that unusual to see filler on cars straight from the factory, be it plastic filler on a body panel or leaded seams. My Plymouth is loaded with factory lead. Also, when properly applied, a high-quality plastic filler should last the lifetime of the vehicle providing it does not get damaged. Lastly, plastic fillers have come a very long way over the past couple of decades. The formulations have improved, and fillers are available that are reinforced with metal and fiberglass.

When it comes down to it, the skill of the person applying the filler is the major factor. A highly skilled applicator can spread plastic filler over an entire body panel and nobody would be the wiser unless the car was repainted or in an accident. In the hands of a, uh… less skilled individual (like myself), a 1-inch wide spot of filler can look like crud.

For an in-depth discussion on the merits and downsides of body filler, I refer you to an excellent thread on the Alfa Bulletin Board. There is photo in the forum post that shows an Alfa with a skim-coat of filler on nearly the entire front of the car and it looks quite good.