OK, I want to start by saying I love OnStar. And, I also love having an in-car navigation system complete with 4-color map. But, when it comes to General Motors vehicles, I recommend that you get one or the other. Not both. I recently drove the Buick Regal, and it had both OnStar and a navigation system. Naturally I tried them both, and I liked features of both. But I have to admit I didn't like either of them completely. I definitely didn't like having them both together.
But, here's a hint: If you're only going to get one, go for OnStar.
The problem with the in-car system is that you can't adjust it while driving. So, if I didn't set the nav before I left my parking lot, I opted to use OnStar, which takes voice-operated commands to set your directions. This is fine in and of itself. But what threw me is that when the directions are delivered to the car, they don't appear in the map screen on your in-car navigation. So, you get the audible, and if you adjust the center display between the behind-the-wheel gauges, you do get a small visual. It just doesn't appear on the map screen. Which, to me, is a non sequitur.
Not that you need the map, mind you. It just seems if you have a map, and audible directions, perhaps it would make sense if they worked together.
Update at 3.52 p.m. on Tuesday, March 6, 2012: After a conversation with Tim Veliu, OnStar location-based platform manager, I do want to offer a small update. Apparently it is possible to download the directions from OnStar's Directions and Connections package into the embedded navigation system. BUT you have to speak to an OnStar advisor to make this happen, and you specifically have to request for this to happen. Additionally, you can change your preferences with the "destination download" so that this happens automatically, but, again, you have to do this through an advisor ... and you have to know the option exists in the first place.
And, speaking of OnStar, it sounds like there is more news afoot. So, stay tuned ...