Knowing how the ear works, hearing is a very complex, dynamic system, but we're just not tuned to notice these kinds of differences.
I've swapped in half-cent cheapo ceramics for mylars for WIMAs and haven't noticed any change whatsoever. Mind you it wasn't a blind test, but if its obvious enough to NOTICE in the same circuit, it exists IMO. I've seen some sites with graphs and oscilloscope readings and other VISUAL representations, but the only variable that matters is how the ear picks it up.
The way I see it, you'll hear more "tone" blowing your nose than you would changing cap types