Surround channels are rarely used, but for light music and effects ambience. The dialog recording sounds dated, but it is still easily intelligible. The soundtrack takes on a strident and harsh quality at times, for example when someone screams or during Regan's loud outbursts. You've Never Seen is quite an improved experience. The entire soundstage is used to envelope the listener, effectively pulling you into the drama.
Music sounds notably smoother and is also more atmospheric.
While the overall character of the new 5.1 EX track sounds a bit dated, it's still very impressive, particularly given the improved fidelity. There are plenty of interesting supplements contained in the 25th Anniversary Special Edition . This piece gives deep and worthwhile insight into the production and public reception of the film. Unfortunately, the commentary tracks by Friedkin and Blatty are rather bland - most of the information they offer is brought up in the documentary and the interview gallery anyway. But be sure to check out the creepy sound effects tests found at the end of Blatty's track.