Finally had a chance to take the Sierra to the dealer for the update. There's good news and bad news.
The good news - The update mostly fixes the popping noise. I can plug the iPhone in and play songs or podcasts, skip from one song to the next all without hearing the popping. So far I've gone as long as an hour without having to disconnect the device due to popping and this was only because I was getting out of the truck. It may be just my imagination but I actually think the sound quality is better too.
The bad news - The popping can be made to happen. If you're listening to a song and hit the FF button for a few seconds the popping starts again and the only way to stop it is to reconnect the device. This also brings up another problem. If during the popping noise you switch over to a podcast (and I can't say for certain if it's just podcast) it will not play. Nothing, no audio at all. The information about the podcast shows on the screen, you can switch from podcast to music but no audio at all from either until you reconnect the device.
Part two of the bad - The charging may or may not work. This issue does not seem to be resolved at all. The first day after the update I could get about 10 minutes worth of charging but then the iPhone would throw up the "Device not supported" message and charging would stop. Also, seems that the first time you plug the device in after it's been restarted the radio will not connect. You have to pull the cable and reconnect. Most times now it will charge for about a minute and quit.
Part three of the bad news - During playback, be it music or podcast, at any given time (I haven't been able to see a pattern yet) the audio from the iPhone drops out, not all the way, just a quieting down for a split second. It's hard to describe but I guess I would say it sounds as if the signal weakens for just a moment and then goes back to normal.
Part four of the bad - Pressing the FF button a few seconds or a few times during the playback of a podcast causes the above symptom of the audio stopping completely.
Am I happy? Somewhat. I no longer have to constantly disconnect the device to stop the popping. Could I live with it with the other problems? Possibly. I very seldom use the FF key so I probably wouldn't have a problem with the popping. Is charging an issue? For me, not really. I usually am in the truck no more than an hour at a time. For me the update is bitter sweet or one step forward and two back.
I've sent an email to the service manager who's forwarded it to engineering so now we wait but at least I don't have to keep reconnecting it to stop the popping. Currently I'm supposedly the only one who's received the update which was done using a USB flash drive in the USB port in the console. Engineering has yet to release this to the general public and I would hope that after reading my email they will go back and have another look before putting it out there so for the moment I'd recommend holding tight. As soon as I hear something I'll be back with the details.