Regarding your comment about files being trans-coded, this definitely is an issue on Windows as the Windows mixer will usually intercept audio playback and muck about with it.
That is true, but all my listing tests were done from within an audio production program, that uses ASIO drivers instead of Windows. That does guarantee bit-perfect playback. I still can't hear a difference.
The best comment I've seen on this topic, is that the sampling theorem was not created to explain how digital encoding of an analog wave form works, but the other way around. The theorem existed before it was possible to do the encoding/decoding, and the math is sound. So when electronic technology got to the point where it was possible to test the theorem, the devices were built.
