The unit also has an internal speaker, and it was louder than the iPhone alone, so hearing traffic directions was easier. The Magellan app allows access to your playlists, and I was able to get some music playing, and while it too was louder than the speaker on the iPhone, I didn't find the volume high enough to want to listen to music that way.
The cradle lets you flip the phone to either a portrait or landscape orientation, so I used the landscape view, which the Magellan app supports, along with most of the GPS apps available. The cradle also has a mini jack for audio out which will allow you to listen to music through your car system if you have the proper inputs.
There were some negatives, though. First, I received messages each time I put my iPhone in the cradle that the hardware was not built for the iPhone, the unit then asked me if I wanted to go into Airplane Mode. I thought that was a bit strange, so I said no, and continued to navigate. I began to suspect that my case was the issue, and sure enough, when I took my phone out of the case I did not get the warning. While my case is pretty thin and seemed to fit fine in the cradle, it is clear that all the contacts weren't lining up exactly right.
Once I had my bare iPhone settled in, I drove around and found navigation was excellent, the turn by turn directions were clearly audible, and it was a lot easier than just having my iPhone on the seat next to me.
I took 2 calls while I was navigating. Neither call was very loud, unfortunately, and at highway speeds one call was almost impossible to hear. I did turn the volume of the cradle all the way up, but it just wasn't enough, especially if the road noise was high. In contrast, navigation directions were quite audible.
With the iPhone in the cradle, power was not a problem, but when I plugged my phone in it had a 58% charge. After an hours driving, I still had only 58% charged. That suggests that the charger is maintaining power levels but not adding anything. My guess is that keeping the screen on and using the GPS full time wasn't giving the iPhone a chance to catch up.
So what were my overall impressions? I think the unit is a lot easier than holding your phone or depending on the built in iPhone speakerphone to hear directions. Although plastic, the unit seems sturdy enough. It was a lot easier to navigate with the Car Kit than without, and I believe the built-in GPS receiver enhanced performance. I really did think phone call volume was just too low, and I expect the promoted ability to work with your iPhone in a case may disappoint some people.
I did try the unit with the Navigon app [iTunes link] (which, it should be noted, costs another $90 to buy), and it worked fine; directions were quite audible. At U.S. $129.99 I find this item a bit pricey, close to the price of buying a small, low end dedicated GPS unit. TomTom has a similar unit at $119.95 and Navigon has a simpler cradle which is just a suction cup and charger. For the price, the Magellan works as promised -- as a cradle with a lot of bonuses -- but it's one of the more expensive options out there. If all you need is dedicated GPS device, you can probably find one of those on sale for about the same price.