In what way? I fully agree that there are other instances of the Holy Spirit overshadowing people in the bible. Prefigurings of Christ such as the mysterious Melchizedek or His presence as part of a prefiguring of the Trinity in Genesis 18 are very well known instances of the Logos taking a human (or maybe angelic) form. I trust you are not suggesting that these prefigurings presuppose earlier incarnations?
The blessedness of the event does not lie in the fact that Mary was so good that God chose her to work this miracle.
Of course not, though indeed it was a blessed event. The Church has never taught that, HD.
As our Lord pointed out, he could have used rocks. The blessedness of the event lies in the fact that God would want to identify with us.
Not simply that He would "want to", but that He in fact did. The danger here for all Christians lies in the Western compulsion to "understand" and "explain" Divine Mysteries, to "rationalize" the Incarnation as has been done here. +Athanasius the Great's "On the Incarnation", the Nicene Creed and the Christological declarations of the Councils of Chalcedon and Ephesus go as far as is safe, maybe in the case of Chalcedon beyond that point, in explaining the Incarnation so that all Christians can accept that the Logos really did become "enfleshed" of the Holy Spirit and the Virgin Mary and became Man, and died for us so that we could fulfill our created purpose, because that's the way God wanted it to be.
The best modern work I have ever read on the theology of the Incarnation is by Fr. George D. Dragas, one of the preeminent Orthodox theologians in the world and a respected friend of mine. It's called "Saint Athanasius of Alexandria: Original Research and New Perspectives".
Here's a link:
http://www.amazon.com/Saint-Athanasius-Alexandria-Perspectives-Theological/dp/1933275006/ref=sr_1_6?ie=UTF8&s=books&qid=1260105638&sr=8-6
If we were to look at the definition of the "incarnation", it means the word became flesh and dwell among us-to coin John. I don't wish to get wrapped around the axle on this because 1) the word did become flesh and dwell among us on several occasions and 2) these events are not considered "the event". The incarnation in scripture is reserved of the blessed event of the Virgin Mary. Yet it remains that Christ did appear in human form in at least several instances in the Old Testament. The ONLY difference I can see between these prefiguring events in the Old Testament and the true Incarnation is in John's phrase "and dwell among us".
The danger here for all Christians lies in the Western compulsion to "understand" and "explain" Divine Mysteries, to "rationalize" the Incarnation as has been done here.
I think you'll find that there are precious few Westerns who understand the incarnation. I don't see any here. Rather, what I would suggest is there seems to be an overzealous danger on the Catholic/Orthodox side to "spiritualize" the Divine Mystery of the Incarnation to such a point it overshadows (if I may use that word) all other miracles of God and the purpose of God. In this zealousness the Incarnation, Mary is wrongfully deified. This is tantamount to deifying Elisha for raising an ax head or Moses for parting the Red Sea.