The only high-def disc that I have (X-Men 3) only has DTS-MA, which currently is not supported by any player (my receiver is not HDMI 1.3, so it requires that the player do the decoding), so I haven't heard what the difference (if any) is yet with my own ears. I'm all for better sound quality though, if it achieves this.
Passenger57, what sort of audio setup do you have?