I've played with a lot of mounts over the years for different devices and gadgets. I have a Garmin Nuvi with a ball socket cradle that connects to the nuvi ball on the window mount, bean bag friction mount, etc. I even used it with a pro-clip mount and other vent mounts, etc. These were all FINE.
Then I found pro-fit international mounts. They make a few different kinds from ones that stick on like others, ones that tap into your plastic of the car for you to decide where it goes, bike mounts, motorcycle mounts, etc. They also make some cradles and universl mounts, etc. However, what got me was called their "VSM G3" mount for my Nuvi. They custom design them for specific car models, and cover a LOT of cars. You can check their site to see if yours is there. They find a spot on the dash or surrounding area where the mount can be attached using existing bolts (i.e. the radio mount) or in some cases they engineer a spot where you can drill into plastic and bolt on. The key is that it's all behind panels or bezels and is covered back up so all you see, basically, is the black ball that is sized for the nuvi mount/cradle. It looks like it is facotry installed for the car.
For mine I used their specific to my car instructions and pulled a bezel off from around the radio with a tool they have to pry it off. That exposed the polts holding the radio in place. I removed one bolt and the metal end of the mount pushed in over the exposed hole. It was a tight and snug fit without putting the bolt back in, which is good because the pressure of putting the cradle on and taking it off isn't torquing at the point with the bolt. I put the bolt back in through the hole of the new mount and tightened it down. The thin and flat metal piece bends over to where the crack, or seam between the bezel and the surrounding panel in my dash is. It is just thin enough to fit snugly in that gap when the plastic bezel is pushed back on. Coming out of that seam is a small flat piece of metal for a tiny bit and then the black rubberized ball. You can clip the nuvi cradle right on to this ball. They also provide what is called a J Stem which is an extender. It snaps on to that ball, and is an extension arm with another ball on the other end. This allows you to have the cradel swing out from where the fixed ball is so it's further away from the dash and can go further in any direction from it to the sides or above/below. Very cool.
The best part is you can buy all kinds of cradles with this socket on it to fit the ball for all kinds of devices. You can also get adapters with the socket on one side and blank flat plastic on the other or a flat square with holes to screw on to, or t slot type clips in all sorts of arrangements for different devices. I thought I would need one of these for the droid. In fact, the president of the company sent me one thinking so too, as he's looking into making a specific droid cradle for this mount upon my suggestion. It wasn't necessary because I have the official OEM car mount. I suppose if you had some universal cradle or something you could get the adapter from him (it has a loose socket that snaps on and a collar that screws over it to tighten down, just like the moto car dock, and a clip on the other side), but with the official car dock you need nothing. There is a collar on the dock where the part that you clip the cradle on to meets the arm for the suction cup. You unscrew this collar and expose the joint that allows you to twist and move the cradle to your desired position. It will now pop off of the arm. This socket will snap perfectly on to the nuvi ball on the VSM and and you put the collar on first and then tighten down in reverse of how you removed it from the offical dock/mount. Now your offical cradle will slide on to this assembly and you're good to go. I use the J stem to keep the droid out away from the dash and further to the side so it doesnt block my radio controls.
The only drawback is that it cost about $30 for the VSM and for the Droid car dock. I got discounts on both, but you might not, so it's pricey. If you have a mount now for your Nuvi that you like with the ball on the end or any other with a ball on the end, getting the car dock from Verizon and using the above method to attach to it will work fine and you can use your old set-up for the droid, but for me it is the VSM G3 and the Droid Dock FTW! It is just really good looking. The mount looks like it was designed into the car, and the OEM cradle snaps the droid in place perfectly while activating car mode. I can position it anywhere and its out of view of theives. If Im concerned I can unscrew the collar and remove the cradle in about 3 seconds and all thats left is the VSM mount and from outside it looks like nothing is there, so there is no incentive to break in.
Here are some pictures (sorry for the quality, some were taken with the droid before the camera started focusing):
The back of the motorola cradle with the attachment plate connected and collar removed (off to the side) with the socket exposed.
The VSM mount with the J Stem extension arm and the plate that comes with the droid car mount (the socket in the previous picture) attached to the standard sized Nuvi ball and the collar tightened down. The cradle isn't snapped on so it can be seen. On your car the mount might be in a different spot. That black arm can be removed completely by simply pulling it off. Then all that is showing is a black ball about 1/4-1/2 inch off of the dash coming from between the joint of bezel/dash. That ball will take the socket from the droid car mount too as its the same size as the one at the end of the J Stem arm.
The same shot with the cradle attached.
Droid in the mount landscape mode.
Portrait mode.
Although it can be easily removed and there is no sign the mount was ever there, it's almost like it's permanant. It doesn't move around or rattle. You can put a fair amount of pressure on it. It is sturdy and doesn't block a vent or damage your car or scratch anything or slide around or rattle.
