The scary part of predestination is that in simplistic form it seems to take free will out of the equation.
The comforting part is that although we all sin and fall short of Gods glory, He STILL choose us!
I think that Paul is trying to convey to a group of gentiles that would have known their status set apart from their Jewish brothers and sisters that they too are chosen and were chosen from the begining of time.
I think he is truely grateful for the work that God is doing in the church at Ephesus. I also think that he is setting a tone with the rest of his letter, one that is going to call gentiles to greater depth and understanding in Christ because of our status with the Father.