I am not Catholic but I believe the Shroud to be authentic. Anyone who watched “The Face of Jesus” on the History Channel recently could not come to any other conclusion. The scientific evidence presented on that program was overwhelming in verifying its authenticity.
For one thing, around the time it first surfaced it was condemned by a bishop as a forgery. Modern apologists for authenticity have explained this as part of a "turf war" for custody, but the fact remains that the contemporary record describes it as a produced work of art.
But belief in the Shroud is not necessary for salvation. If it's a help to somebody's faith, that is a beneficial thing. And think of the miracles attributed to icons!
I like BXVI's approach; it makes sense.