I just bought and received the car dock for the Droid 3 and just wanted to give everyone the details about it.
First of all all of the contents. It has the dock, the windshield mount, the dashboard mount, a combination usb micro/3.5mm cable, a separate 3.5mm cable. Sadly it does not have the dc to usb adapter... I had to go out an buy one for $10
The phone fits perfectly in the dock and the dock has a removable plate inside to allow cases to fit. Phone did not vibrate and was very sturdy in the dock. One thing I did notice is that you have to lightly push the phone down to make sure it is fully on the micro usb plug. If you just lets it slide in there it does not fully plug in, very minor inconvenience. And it uses the standard ball mount so you can swivel it wherever you want to.
The cable was one part I was not expecting, it is a combination usb/3.5mm cable. it plugs into the back of the dock, but unlike the droid 2 dock it goes in sideways and has kind of a cable feed built into the dock; which I find much better. At the end of the usb cable it's a standard usb port but there is an additional port immediately off of it which is a female 3.5mm adapter. I personally use bluetooth for the audio but the fact that it is there and they give you the audio cable to go with that is pretty nice. and the cable has a little piece of velcro off of it so you can organize loose extra cable.
Last thing is the motorola car navigation software is horrible... absolutely horrible. It was extremely slow, did not give me the options that I wanted, and refused to work with the new google music which has all my music streaming. I found you can download the standard google car dock apk, install it with no problem and set that as your default for the car dock. Was a huge upgrade compared to the motorola dock software, worked with everything and was extremely quick. here is the link in case anybody else wants it http://www.droid-life.com/2010/10/01...-car-home-app/.
Overall, it is a really nice dock. My only complaint is that for a $40 car dock their is no car charger bundled with it.