From what I've read, people are having problems using both the Kenwood dnx8120 and iPhone bluetooth.
People say that it sounds fine in the car, but sounds choppy to the person on the other end. I just came across this update and several people said that it solved the problem.

I am going to try it out for myself very soon.
...thought some people out there would like to know about this, if they didn't already.
http://rs82.rapidshare.com/files/137...honeUpdate.zip

 

I'll have to try this.