In a preview editorial for the summer issue of Sacred Music, William Mahrt writes on the Apostolic Exhortation, and makes a different point than I've seen. He says that the sweeping radicalism of the document is to assert a different liturgical focus than that which has been common for decades. Benedict XVI confronts a fundamental reality head-on: the liturgy is always and everywhere Christocentric.
If this "were understood well, our everyday liturgical problems would admit of much easier solution. If beauty is a compelling need in the liturgy, then we must choose the most beautiful music possible. If the focus upon Christ is the all-encompassing theme, we should comprehend more easily the reasons that the pax should be given with reserve immediately before we are to receive him in the sacrament. Pope Benedict draws such practical applications, including some quite specific recommendations for the use of chant and Latin."