I can share with you my personal experience. When I decided to purchase adapter for cars AUX Link, I compared all the prices and it's really cheaper to buy it at the official online shop
http://auxcarkits.com/. It was delivered in just four days. At first I decided to try to install it on my own, but had troubles taking out the car stereo. I didn't have necessary tools, so finally I had it installed in the nearest autotuning center. It took around 15 minutes. So far I'm totally contented with this kit.
Advantages:
- compatible with iOS gadgets, USB pen drives, SD, but there is also a 3.5 mini audio jack for other mobile devices (MP3 players, Windows-based and Android-based smartphones, tablets, laptops, netbooks, PSP etc.).
- high quality sound
- you can use it as a charger
- with additional Bluetooth module can be used as a handsfree car kit
- music control with steering wheel buttons and buttons on the car head unit (very convenient)
- compatible with all music formats
- delivery is free and fast
- occupies very little space and almost invisible
- now I can listen to all my favourite music without carrying piles of CDs.
Minuses:
- relatively expensive as I also purchased additional Bluetooth module to use the adapter as a car hands-free kit
- couldn't easily take out the car radio so I had to go to auto workshop
But taking everything into account, I think it's a good product. So in my opinion it's worth purchasing.