In looking for a 2013 Honda Civic (LX model, no Navi), the text feature was very interesting and important to me. Why not have my texts available on the dash and read to me rather than messing with my phone. Anyway I won't go into the whole thing about safety while you're in your driving and all that. We all know what we should and shouldn't do. Anyways...
I spoke to a salesman who said that this feature was not compatible with the iPhone, only BBs. Of course this didn't impress me and I found it hard to believe that Honda would restrict themselves like that. Anyway, a few searches on the web later and Honda shows that the iPhone 4, 4S and 5 are compatible for receiving texts through the car, just not sending them. I believe you need a minimum of iOS 5+ for it to work though.
Once I found this the salesman and I did some testing with our phones. He has a 4S with iOS 6.1.3 and mine is a 4 with iOS 6.1.3. Initially we setup the phone using the Bluetooth config on the Civic's iMID display. It was setup and hands-free calling tested o.k. Next the texting was tested. Both of us have iMessage turned on. Neither of us could get the messages we would send each other (1 of us had our phone setup with the car, the other sent the text and vice versa). The messages were received by the phones, just not the car). When we would go under the Text Message section, it would say "Unsupported Device". I knew that couldn't be as Honda said it was compatible. After more web searches and a phone call to Honda by the salesman, I found the following.
1) It seems like the person who had their phone paired with the Civic had to disable iMessage to start getting texts. The salesman still had it enabled on his though when he sent me texts (as SMS) and the Civic got them so both people aren't necessarily required to disable it. Now under the Text Message section, it would list the messages received.
2) I changed the Notifications on my phone for Messages from Banner to Alerts. Once I did this it started to work. The texts were showing up on the car. I had read where another person had tried this successfully but then changed it back to Banner and it continued to work. I experienced the same thing.
Granted this wasn't extensive testing but I was able to get it to do something closer to what I wanted. I'm not sure why Apple and Honda can't put their heads together to make sending texts work on the car but maybe someday it will work when enough people complain. It's kind of a disappointment that I couldn't get iMessage to work but I haven't given up hope yet. As it's a proprietary protocol, I can see Honda not supporting it though.
Hope this helps someone out!
FYI I bought car!