I've got it now. Tried out Spatialize. Head tracking works really good. It does a good job of keeping oriented to my head. I can wave the phone back and forth in front of my head or set it on the table next to me and it doesn't move with the phone- only with my head. It seems to mostly affect the material that is mono (which is usually vocals or lead guitar solos). And that center material has some sort of slight phase shift or reverb on it. Not unpleasant, but not a terrific improvement either. Naturally, they make sure that Spatialize is louder than without so it's hard to do a direct comparison.
I have to say, I'd like a whole lot more from this. Hopefully the OS updates will add stuff incrementally. What I'd really like to see is some sort of HRTF calibration so I can actually hear distance and rear channels properly. It still sounds like a straight line through the center of my head like stereo... just a little less abrupt left or right, like with crossfeed.
