As I understand it, it prevents you from having to crawl underneath the car to adjust clutch cable. As it stretches (if that is a good term), you can adjust play in your clutch at the firewall instead. I have one with the double hook quadrant thing and like it. I dont know how to explain it but I have a better feel for the clutch now.
My friend has the exact same car I do... 02 GT... and his clutch pedal is soft like butter, and my is really stiff. Does an adjustable clutch cable have anything to do with how the clutch feels?? We both have stock clutches... etc... and I always wondered why there is a difference. I can shift his car a lot smoother too... could my cable not be adjusted properly?!?
The stock cable is self adjusting. So if you drive your car harder the clutch will tighten up and fell more stiff, then after normal driving it will adjust again and loosen up a little. For myself, the biggest advantage to this is at the track. You know that the clutch pedal is going to feel the same on every run.