A fellow trad was concerned that in some Catholic circles the divine mercy prayer (prayed on rosary beads) was replacing the recitation of the Holy Rosary. If true it would be a very serious concern. As well, an SSPV priest noted that rays on the divine mercy picture of Jesus are replacing the image of the Sacred Heart, of course veneration and devotion to the Sacred Heart is an ancient Catholic devotion. There's also a New age aspect to the practice (imo) in that it is strictly a message of mercy with no meditation or contemplation of Our Lord's Justice. As a wise traditional priest once told his flock.... "God is perfectly merciful, however He is also perfectly just".