Call quality has been good in fact better then the i730 because my boss could hear me on the 8525 yesterday at the game, where it was very loud. While using the i730, he always told me I mumbled. However, there is a difference between GSM and CDMA when there is not much signal. On the i730 with no bars showing I can still place a call and have a conversation. On Cingular and T-mobile phones 1 bar means choppiness. I am think it is because of the differences in technology. I firmly believe CDMA is better in real world use and technologically more efficient. The nice thing is that I haven't found many places where the phone didnt work. Cingular has the train tunnels underground covered in Center City Philadelphia. I could make calls in the tunnel and people were looking at me funny.

Hope that helps.