(Despite the title, this has nothing to do with the previous post.)
To begin this post, a reminder, these musings are simply my prayerful reflections on my own experience of celebrating the Holy Sacrifice of the Mass, I am not attempting to offer any strict theological arguments. If you are looking for theology on the subject, check out Turning Towards the Lord by Fr. Uwe-Michael Lang, and The Spirit of the Liturgy by Pope Benedict as two starting points.
Although my priesthood is still somewhat in its infancy (having not yet reached my second anniversary), I have had the opportunity to celebrate Mass ad orientem (facing the same direction as the congregation) on a number of occasions. The vast majority of the Masses I have celebrated have been versus populum (facing towards the people), but I have celebrated perhaps a dozen Masses turned "the other way around". You might be thinking that I am referring to the Extraordinary Form, however I have only had the opportunity to celebrate that form of the Mass twice. The other perhaps ten times have been Masses celebrated for small groups, but in the Ordinary Form, and in English.
The first of these occasions was after just a month of ordination, and just this one experience gave me a profound change of outlook on the way I celebrate Mass. Saying Mass with the congregation behind me, demonstrated to me just how much I felt the need to "perform" for the people in front of me when saying Mass facing them. My awareness of that came largely through the absence of that desire when facing the other way. If I had never celebrated Mass ad orientem, most likely I would never have noticed.
Of course I have heard the classic argument that when the priest faces ad orientem it inhibits participation, but remember, these were Ordinary Form, vernacular Masses, the people were still making the same response, saying the same prayers, hearing the same words, I was just facing the other way (of course we could get into the true nature of "participation", but I'll leave that for another day). Likewise, I was not up there "doing my own thing" as often claimed of the Extraordinary Form, I was very much aware of the congregation behind me, even if I wasn't looking directly at them.
As I began to reflect further on the experience, I also recognized a greater sense of being (wait for it...) the servant of the people when facing ad orientem. When facing the altar, I was now facing God, I was there on behalf of all of the people gathered behind me, I was offering the sacrifice of the Mass to God, on behalf of the assembled congregation, I was not there as the "leader" or the "presider", ruling over the people from my chair three steps higher than everyone else, I was there as the intermediary between God and his people, offering the sacrifice for the sins of the people.
Once again, I will remind you that these are just my own musings, my own subjective experience, but I would challenge my brother priests, just try it, once or twice. Make sure it's in a church (if there's a tabernacle in the centre so much the better), make sure you have at least a few people in the congregation, not just you and a server, do it in the Ordinary Form, do it in the vernacular, then reflect on the experience afterward. You just might find it changes your perspective on things, in more ways than one.