I recently posted a story about how the VDC saved my butt on the way to work. I took an exit with a sharp curve way too quickly in the rain. I usually drive in the mid-80s, so when I slowed down to the mid-40s for this curve, I thought that was slow enough. No way. I got into the turn and the rear end immediately let go. It just went right into a glassy-smooth slide. After about 5-10 degrees rotation, the front let go. After the front slid a few inches to the left, that's when the VDC kicked in.
I felt the front left and both rear brakes get applied on their own. The g's shifted sharply to the front left corner. The VDC immediately recovered from the slide in time for me to execute the second half of the S curve without incident. The whole incident lasted between 3 and 5 seconds, although that is probably a long estimate. It happened very quickly. The end started to come around, the front let go, the VDC saved it, the car dove to the front left corner on its own, and then I had slowed down enough to execute the second half of the exit without incident. Whatever the VDC cost me, I'm sure it saved me more in axle, wheel, and frame damage and lowered resale value as I was heading for a fairly tall concrete curb at the time that would have ruined my day.
The first time I felt it, though, was during the first few weeks of having the car, when I hit some loose gravel exiting a highway. I've been used to sliding through that gravel for many years, so it was a little shocking to feel just the front left brake apply on its own (and take all the fun out of that exit

) If you regularly do "spirited" driving or have to face wicked ice every winter, its quite worth it.