Well I used one for about a year. But each time you get in your car you have to place the tablet in its (custom made) mount, connect it to the power and stick the usb cables in.
So its easier when you have a regular install.
Now when I start the car, my screens comes up from my dash and my laptop automaticly starts.
I might go for the tablet again if I was able to use its regular mount so I didnt have to put in all the cables all the time.