KenpoTex
Senior Master
This is the technique I was taught. I don't fully rotate the gun until it is even with the centerline of my chest. By the time it's rotated, both hands are in contact with the gun. At this point, It's just as fast to draw and rotate at the hip, using less efficient muscles (for me, anyway) as it is to bring the gun straight up, then rotate with it in the center of mass, with two hands already on it. That's why I was saying earlier that if I simply "shoot earlier in the draw" I'll just hit the ground.
If the attacker is at arm's length (or even a little more), you'll still get a hit, it'll just be lower in his abdomen. I like this method for extreme close-quarters because you have the benefit of knowing exactly where the weapon is pointed thanks to the kinesthetic awareness you've ingrained by using a set of consistent reference points.
The other method of rotating the gun right out of the holster probably is better (i.e. slight decrease in the time it takes to get your first shot off) if the oponent is farther away (2 yards+). However, for me, the benefits of the high-elbow, muzzle-down retention position I mentioned above outweigh the very miniscule advantage in speed of the "rotate immediately" technique. YMMV