They were clearly changed men. As our pastor pointed out in today's homily, Peter, who was certainly not know for his eloquence and who had denied even knowing Jesus, is now able to give an impassioned speech that converts thousands as he boldly proclaims Jesus' teachings and miracles. As he and the others proclaim the Gospel, people of all different nationalities are able to understand them in their native languages. Here, then, is the beginning of the Christian mission--the true birthday of the Church.
Christian religions have not all had the best track record. There are plenty of instances of atrocities horribly committed by people who claimed to be doing God's work even today. However, the message of Christ is still the greatest one that our world has ever known. Spreading the love of God and the message to love and forgive one another is a mission that is always relevant. Had it not been for that blessed Pentecost almost two thousand years ago, we would have never known it.