I disagree that this is a Sprint Issue.
I have
two Sprint phones at the moment
I just tested it making calls to each phone back-to-back.
The call to the Android HTC Hero from the other had a delay.
When I used the Android HTC Hero phone to call the standard Samsung flip phone, it was almost immediate.
Hence, I am more inclined to believe that this is not a Sprint network issue, clearly a phone issue.