[rem1313]

iMessages has built in notification to the sender if the message has been delivered to the receiver, hence the status "Delivered" or (if receiver has opted-in) also Read status. I see no point in this feature, since the phone could be dead for various reasons, not just battery

[k33l0r]

It would be nice if the delivered indicator could be relied upon, but it seems to report that a message has been delivered once the Apple servers have received it, not when the destination device has received it.

This is especially noticeable under poor network conditions (I think I first noticed it at a music festival where even regular SMS messages struggled to get through due to network congestion).

[Terretta]

Nope. It needs to hit a device to say Delivered.

For example, if the recipient is out of 3G data coverage but can fall back to SMS, you won't get Delivered, you'll get a line across your conversation denoting a switch to Text Message and a different color bubble.

(Several people I message are in marginal coverage areas several hours a day, so I get to see this in action daily.)