Many of my priest friends have visited Medjugorje. If it wasn't for the fact that the Bishop of Mostar has forbidden it I would be tempted to go. My friends speak of the ardent devotion of the pilgrims, the long lines of people waiting for confession, stories of young people keeping long vigils before the Blessed Sacrament and profound attendance at not very well organised Euchartistic Liturgies.
These are things that one would expect at a place where the Mother of God was present. Prayer, devotion, ultimately holiness ratify an apparition. For Catholics there is an element of believing the message because we believe the messenger. Even the Lord himself is believed in because the Apostles were and the Church is a credible witness. Lourdes, Fatima, the revelations of the Sacred Heart, of the Divine Mercy are worthy belief by the fruit they produce, first of all in the primary witness of the Apparition and in their followers. It is perhaps very significant that none of the visionaries have received or accepted a religious vocation.
In a document issued by the Bishop of Mostar, the bishop speaks of schism in his diocese, of violence, of feigned sacraments, I know the document is now 5 years old, but it is still relevant. There is one account of the friars inviting an "Old Catholic bishop", that is not some one in communion with the Holy See to administer Confirmation, he gave the "sacrament" to 800 individuals in three parishes, later it transpired he was not even a bishop.
This I find is actually the most shocking revelation of all, and seems directly related to general sense of disorder and disobedience in the diocese of Mostar.