I've done this for various projects, including SW, in Vegas. Something like a 4% slow-down would not be very noticeable. IIRC, once you start getting past a 1 to 2 second difference (between the master soundtrack and the converted soundtrack), you start hearing audible artifacts (i.e. generally unnoticeable or dismissiable sounds, such as clicks, start developing more of a presence, and can interfere with one's recollection of how the audio should sound.)
As to speeding it up, I don't think it would cause as much of a problem - except to really anal people with perfect pitch.
(j/k!)To be honest, I myself, would probably notice that it was sped up, but that's just me. I think all audio should be played at 33 1/3.
