Having just picked up a 4S, I wanted a Car Kit that both kept the iPhone secure, and also looked good, and I'm happy to say the Navigon Design Car Kit is the business.
The fit is good and snug, and although I would have liked a bit of padding around where the kit clamps onto the phone, I have found that if you take a few seconds more to carefully seat the phone in the holder, you should minimise the chances of scratches.
Like a few other reviewers, I bemoan the fact that the adjustment for the holder is done by loosening/tightening an allen screw (not supplied) I actually had to go to my local DIY store to buy the right key as non of mine fitted. I now keep this key in the car, but since I set it up originally, I have not had to tighten it.
I use my Navigon on the dash, rather than the windscreen, and have found it to be very stable over some pretty horrible road surfaces. The level of adjustment is fine for my needs, and the provided usb cigar lighter adapter and lead look to be of good quality.