Gorgeous it is and as rare as hens' teeth! But as a layman one can get away with saying: "Holy Father, bring back all the old vestural privileges for monsignori, canons, bishops, etc. which made it all so fun!"
In the Rome of today it is extremely rare to see the mantelletta anywhere (even at St. Mary Major anymore). This is because of concelebration, the fact that the mantelletta is reserved to the very highest class of monsignori who are protonotaries apostolic de numero, auditors of the Sacred Roman Rota (as is the cleric in the photo) and certain chapters of canons, etc.