I had a chance to use the X Car mount for GPS today... i have to say i'm disappointed honestly...partially for the GPS App, and some because of the charger on the dock.
I had to reboot the D-X to even get the GPS to find ANY signal (not the car docks fault)...
After a while of being up on the dash, plugged in in an offical Verizon micro USB Car Charger in the back of the dock, it just stopped charging...I'm guessing it might have got too hot (battery was REALLY REALLY warm to the touch). Once I yanked it out of the dock and put in a cupholder (out of the sun), it started to charge again... not sure if that was the charger or the phone/battery.
After that I, while the charger was plugged in, I couldn't keep a charge on the phone...it finally ended up being about 30% at the end of our trip (while plugged in the whole time). Again, probably phone, battery or charger isssue and not the car dock, but since I couldn't use it for more than 1/2 of my 400 mile trip for one reason or another, it was ultra disappointing.