imsohappy ~ I've heard almost exactly the same speech in relation to AEPhi. It's not so much a reflection on a specific sorority, as it is about having a sisterly bond in general. You find the right house, be it AEPhi or Kappa or whatever, and you know you've come home.
ChiO ~ I think it just depends on what your sorority does for pref. In my chapter, not everyone gave a speech, but everyone had a role - reading a poem, or leading everyone in a song, etc. I think this was b/c we were such a small group (~20) - in a larger chapter, it wouldn't necessarily be the case that everyone would say or do something, other than join in the songs.
DeltaBeta ~ I wish I could give you more specific help, but I joined via COB, so I've only seen my own sorority's pref ceremony. We did do letters - one sister reads a letter she's written to another sister who's touched her in some way (helped her get through a difficult time or whatever). It's a surprise to the other sister. And there are usually lots of tears...