I recently purchased an iPhone and also purchased the Navigon navigation software so I can use it as my GPS in the car and hand over my Garmin to my wife. So now I have an all in one solution for music, GPS and phone all streamed to my bluetooth enabled car stereo.
I purchased a cheap iPhone cable, mains and car charger. Although the mains charger with the cable works fine as does the cable hooked up to my laptop for syncing, the car cigarette adapter did not fair very well. It was made of a rather cheap plastic and after about 5 minutes it got rather hot to the point where it stops functioning. It also had a tendency to fall out of the cigarette socket as it was fairly loose to begin with.
I searched for an alternative solution and found the Powerjolt Dual. Although I could not find any reviews for it online, I did read a review of another Powerjolt without the dual USB connections and it was very well rated. I plumed for the dual version.
I have to say I am very happy with this product. It is made of a sturdy plastic, does not look or feel cheap and even after an hours use in the cigarette socket in my car, it did not get hot. It charged my iPhone to completion even whilst the GPS software was running. It also has the added bonus of a 2nd USB connector, so you can charge any other item, say a camera or any other product that charges off of a USB cable simultaneously. It also has a nice touch of two LED lights which go around the circumference of the top of the charger and light up depending on which USB connector is actively in use. It fits in very well in to my cigarette socket nice and snug and does not feel loose.
Highly recommended and very good price point too.