According to Mgr Oswald Gracias, archbishop of Mumbai, the Motu Proprio will “have two important purposes.”Based on my limited personal experience ... if this has even a tiny effect on adding solemnity to the celebration of the Mass, it will be good!
“One very important purpose will be to renew and enrich the liturgy, reclaiming the liturgical form that existed before the Council, which is a great heritage in the history of the church,” said the prelate who is also an expert in Canon Law.
“The Motu Proprio is a sign that the Holy Father wants to make available to the Church all the treasures of the Latin liturgy that have for centuries nourished the spiritual life of so many generations of Catholic faithful.”
“Secondly,” he explained, “it is a response to the pastoral needs of the faithful. In Mumbai, Cardinal Ivan Dias (Gracias’ predecessor) had shown much pastoral sensitivity in allowing the Tridentine Mass. However, there may be practical challenges since there are not that many priests who know Latin.”
Tons of links to reactions at the Summorum Pontificum blog.