No, iMessage doesn't completely replace SMS; but I know 95+% of the messages I send and receive are iMessages. That has to have hurt the carriers' ability to sell unlimited texting plans for $30 a pop to those that don't already have a plan that has unlimited texting bundled in. I have a Verizon Share Everything plan and I wish I could drop it down to 200 SMS messages a month and shave $20 off my monthly bill. Unfortunately, they don't give me that option.
I don't really know what to say to that. We've had an unlimited text/data plan from Sprint since Christmas of 2008 and before that it was a Fair & Flexible plan that had us at 1000 shared text messages per month. Before that, we didn't text so we've never paid seperately for text messaging.
Apple wanted to create a messaging experience for its customers that was unique compared to what the carriers can provide. Everybody else who's not an iOS user has to use only what the carriers offer for SMS.
If you are saying unique, in that Apple handles it, well OK. But, the only difference I have ever seen between iMessage and standard text messaging is the fact that the color bubble changes from green to blue.
I can count on two hands the number of people I iMessage. Except for my sister and a few friends, most of those people live outside the US. In that regard iMessage is great because it's saved me on international texting charges which my unlimited plan does not cover. I don't have a lot of people I iMessage because most of the people I know don't have iDevices. One person I know has an iPod Touch and could use iMessage, but doesn't.
I also have a Google Voice number and the ability to use Talkatone for free texting, which I have done in the past when I was using my iPhone 3GS as a backup phone (it's WiFi only).
My point is that if Apple was to truly threaten the carriers with iMessage they would have found a way to completely replace standard text messaging to any phone (iDevice or not) using iMessage. They didn't because doing that would have cut the carrier out completely and they can't do that and still sell iDevices.
Apple could/should take the same stance with DnD. They can create a better experience for their customers than what the carriers can provide in terms of giving the user more control of who can reach them. Everybody else who's not an iPhone user will have to stick with managing call blocking via their carrier's website.
I don't disagree with you. But Apple is all about more control to Apple, not the user. I would love to be wrong, I would love Apple to fix DND and make it a true call blocking feature at the phone level. I just don't see that happening though.