In some small sectors of the sacred-music community, there is a persistent debate about Mozart and Haydn Masses, whether they are too elaborate for a sacred setting or whether it is a myth that Pius X attempted to diminish their status.
For my part, I find this whole debate, a real blast from the past, to be completely irrelevant in times when the average parish offers a musical fare that is not recognizably Catholic or liturgical by any stretch -- something which is changing but not nearly fast enough. Mozart is a wonderful respite from this, a welcome elevation in every sense. Given the realities of the present day, let's save the "orchestral Mass" debate for a 100 years from now.
In any case, it does no good to argue this stuff abstractly. The best approach is to attend a Mass at, say, St. Agnes in the Twin Cities, and experience it yourself. If you have doubts, I suspect that the experience alone will wash them away.
Also, I'm happy to see that there will be a full orchestral Mass with Mozart's "Sparrow Mass" at St. Mary's in Kalamazoo, said according to the 1962 Missal. The data is November 23, 2008, at 12:15pm.
Here is a video of Sanctus/Benedictus, and you will see why the Mass acquired the "sparrow" designation.