With Windows you can define a buffering time, and there's the possibility of setting it up to zero. In Mac I didn't find this option. In any case, I think you always get a small delay in the sound, but I didn't used it yet for movies so I cannot be completely sure. I'll try to test it today and come back with an answer, but initially take it like a “yes" of around 0.5s.
Edited by Ashade - 3/7/13 at 7:14am