I've never really thought much about the timing of Pentecost. It would have been an entirely different start to the church if it had not been during a feast in Jerusalem. The exquisite providence of God brought people who spoke other languages, who would notice and appreciate the tongues spoken that day. The festival collected the seeds of the church throughout the whole region. It selected devout people, who would be most interested in the message, not just some random passerby! God was completely sovereign in the timetable of the birth of his church.
Peter lifted his voice and spoke. It is the same verb, an unusual one, in Acts 2:4 and Acts 2:14. Clearly, we are to understand the connection between being filled with the Spirit and speaking boldly.
Young men will prophesy and old men will dream dreams. Interesting. Isn't it the other way around naturally?