First, let me start off by saying this: I am not among the group that think the Ordinary Form of the Mass is invalid or illicit. While some Masses have the potential for being illicit, just because it's not the Latin Mass (known as the Extraordinary Form of the Mass) doesn't make it automatically invalid. Not every Mass needs to be in Latin, have incense, or Gregorian Chant. But it does require reverence and not to be confused with entertainment.
The biggest problem I have encountered (until very recently) are the choice in hymns. As some have pointed out on various message boards, the songs we sing at Mass either are banal, or may not completely reflect orthodox Catholic doctrine. Some are just plain silly; for example, "Sing A New Church." My reaction is this: Is the Catholic Church not good enough? Didn't we go through that with the Reformation? Give me the hymn, "The Church's One Foundation" any day.
But a couple of weeks ago, I encountered something that would make the problem of some hymn selections seem minor in comparison. We had a guest priest who celebrated Mass at every Sunday Mass, including the 6 PM Mass which I attended. While the homily was good, the rest of the Mass left much to be desired. The main problem was that he would play around with the words outside of the Consecration. For example, normally the celebrant would say, "The Lord be with you," and the response would be "And also with you" (faulty English translation, but that's for another time). Instead, he would say, "The Lord is with you," and we would give the customary response, and he would say, "Your welcome." Sorry, Fr., but the Mass isn't meant to be entertainment, and you're not the star.
Fortunately, he didn't play around with the Consecration, but attending that particular Mass left me at unease. Our priests and our bishops have great responsibilities as shepherds for their flocks. The Lord trusted St. Peter to "feed his sheep." With a great mission, comes great responsibility.