I use mine as a reference point for after doing a reload especially in the middle of a stage I know exactly where I will be gripping the rifle again.
However most people use a vertical grip wrong, as in they hold onto it like a tennis racket, which is like you said, designed for recoil management during sustained full auto, but even then its not idea.
I grip the rifle in front of the vertical grip, basically only indexing my pinky and ring finger against the front top section of the vertical fore grip, and still gripping my fore end with my middle finger and pointer under neath, and my thumb wrapped around on top, almost fully extending my elbow.
This is the "newer" method taught by some top instructors today to dampen recoil a little more, but mostly like mentioned above, to be able to snap the front end of the gun to the next target with out over swinging. It is NOT the most comfortable at ALL however it does work quite well for what it is designed for, shooting under stress either from combat or competition.
Companies now are making "hand stops" for what I use my vertical grip as, however I see no point in investing in something that I already have covered with my vertical grip at this moment.
I will say the Magpul Angeled Front Grip takes some getting used to at first, but once you get used to it, and the method described above, it is quite comfortable and works very well.
By no way am I suggesting this is the only way to grip an AR, but it is becoming pretty wide spread. Here's two videos you can see it being used to get a better look if I didn't type it out well enough.
http://www.youtube.com/watch?v=5esr2vix6QI
http://www.youtube.com/watch?v=tYjitNIEmzw