I have tried plain flour. However, the issue isn't so much that it is "pizza flour" or "bread flour" or whatnot, but rather the strength of the flour. Usually, "pizza" flour is stronger, because it can stand longer fermentation times (think 48+ hours), which is why it is desirable. I am aware that many italians use regular flour, with great results; however, the fact that plain flour cannot hold long fermentations makes its use limiting.
I agree that pizza flour is mostly smart marketing, provided a) it is used as if it were plain flour; b) it is used without concern of its actual perks; or c) it isn't really pizza flour, but rather normal flour with another label, which is precisely not what I am after.