Today midnight (at least, if the postal datestamp is still a legal proof), postal rates are modified for mail sent from Metropolitan France, the four Overseas Departments-Regions (Guadeloupe, Guyane, Martinique, Réunion) and in two Overseas Collectivities (Saint-Barthélemy and Saint-Martin). In brief, where La Poste operates and Phil@poste is sole master on philatelic issues.
A too little one eurocent more for the most known rates: 0.55 euro for a less-then-20-gram letter nationwide will become 0.56 euro. More centimes elsewhere, in multiples of five: more easy to cash at the counter.
Because I send mainly postcards to the European Union (0.65 > 0.70) and the world (0.85 no change !?), thank to Postcrossing, my problem is not the cost. Indeed, lucky I am not to have to weight my centimes on stamps against the ones needed to buy nutritive but perishable food. But I don't forget to catch the dozen of good euros I can when looking for high value goods.
My worry is practical and political. For the latter, my refusal to use Nicolas' Marianne stamps obliges me to manage my 1, 5 and 10 cent stamp stock of the smiling Frenchs' Marianne by Sir Lamouche. Until the arrival of an allegory more republican, democratic and open to the future (yes, I am an utopist or a naive).
Practically, the half-sheet presented above plus the stock already purchased may help me to spare one cent stamps (0.56 + 0.10 + 0.04 = six stamps on a postcard or one cent gift to La Poste) and to use with reason the 5 and 10 cent stock (0,55 + 0,10 + 0,05 = 3 stamps and that makes a pretty postcard to a European neighbour, despite the lack of European rate commemorative stamps).
In conclusion, I regret the Youth Collection (example) that gave 20 and 30 cent stamps. They helped fixing good franking to foreign penpals.