Okay folks, I tried the Ding King. Here's the verdict...
It did improved the ugly appearance of the ding but when pulling the ding out, you actually pull out the sheet metal so you can see a small "bubble" instead of flat smooth surface. The kit also supplies a detailing stick for you to smoothen or knock down the "bubble". However, if you are not careful, you knock the ding in again...
Yes, this darn thing requires many tries and ample patience.
The dings on my door are sharp and small so it was difficult to achieve near-perfection results. If the dings were slightly bigger (size of a quarter), I believe the improvements would be more significant.
I didn't have my digital camera with me so no before and after pics were taken...