You mean when the call gets connected, or is answered by the person whom you're calling?
I think it is a nice feature, so that you don't have to hold the phone next to your ear and wait for the other person to answer.
It seems to be a feature to let you know that the call has been connected. That way you don't have to sit and stare at your phone until it says connected then put it to your ear.
This is something Windows Phone 7 did as well, FYI. It's not limited to this hardware, it's an operating system feature to let you know the call is connected.