People feel so strongly about liturgical music, and most of the people who seem to be reading and posting on Catholic blogs feel strongly negative about most of the music they hear in Catholic Masses.
(And I am careful not to generalize to the broader Catholic population here. There are plenty of folks out there who love the music that many of the commentors and bloggers despise. I am always reminded of this when I'm unfortunate enough to be present when Let There Be Peace on Earth is used - usually as a final hymn, correct? And the congregation usually blasts it - unlike any other piece in the repertoire. That part that makes me want to pour lye in my ears ...to taaaaake each moment and liiiiiiive each moment in peeeeeace eternaleeeee-eeeeee! ...usually raises the roof. So go figure, and don't generalize, is the lesson of the day.)
But the real point of the post is not to pit one form of music against another or argue about which is better or prettier or more reverent...it calls into question the very purpose of music in mass. And I think Fr. Vidrine summed up the idea nicely with a comment he made on the post, "Simply stated, the Church calls us to SING THE HOLY MASS, not sing AT Mass." This is a pretty new idea to me, and one I'd like to read more about. As much as I love the old traditional hymns, perhaps even those are not technically the best way to make the mass into a "seamless whole."
On a related note (bad pun alert), one point that was made in the comments that I very much agreed with was that, the way hymns and praise 'n worship type songs are used in many modern masses (say that five times fast!), it often ends up seeming more Protestant than Catholic, more of a collection of disjointed songs and spoken prayers than a unified whole, and that's really quite unfortunate. I'm certainly not even close to being an expert on this issue, but it would be something if our liturgical leaders could help us find the intended use of sacred music in the liturgy so that we could all experience the mass at its best, and perhaps that means learning to sing the mass instead of just singing at mass.