Its been there since the beginning, but the device has to have it turned on in iMessage settings in order for the sender to see it displayed as read once read.
Wish it would default on.
P.S - Orlando?
While I agree, I can see why Apple chose the default to be "off". If it were on by default, people would complain that it's a privacy issue, even though you can turn it off.
I believe blackberry defaults on for BBM.
P.S - Orlando?