The BD does include the mono track so purists are safe for the most part. Me personally, the mono track on the BD is good but the mono track on the 2005 DVD was slightly crisper. Lately Ive been comparing the BD Mono track, the 2005 DVD mono track, and the mono track from a 1990s LD and noticed some things.

After Chrissie’s attack, theres a shot of a wave rushing over Cassidy. At one point we see his mouth moving. On the LD mono we clearly hear him burp. On the 2005 mono and the BD mono, you only hear the burp if you listen very VERY carefully. The burp is missing completely in the surround mixes.
In the scene where Hooper cuts open the Tiger shark, at one point he pulls out a coffee can followed by a license plate. On the BD mono, the sound effects of these items hitting the floor are about a split second out of sync. On the 2005 mono and LD mono, the sync is identical.
The dialogue being shouted when the shark is tugging the boat is more audible on the LD mono as well as the surround mixes. On the 2005 mono and BD mono some of the dialogue is nearly drowned out by the water crashing as well as other various noises.
The sound of the engine exploding is in the wrong pitch on the BD mono. On the LD mono and 2005 mono, the pitch is identical.
There’s a noticeable drop in volume during a shot of the shark ripping the cage apart before the rigging snaps on the BD mono. This doesnt happen on the 2005 or LD mono.
Brody’s scream when the cage rigging collapses is louder on the LD mono as well as the surround mixes. You can only faintly hear it on the 2005 mono and BD mono.
The surround mixes and mono tracks on the BD and 2005 DVD restore a line thats not on the LD track. When Quint raises the cage to the surface and he and Brody clearly see Hoopers gone, earlier in the shot we hear Brody whisper ‘yeah’. This is more audible in the surround mixes but missing completely on the LD.