In our experience, most active 3D glasses are sensitive to head position or, more precisely, head tilt. With most of them, however, the effect is minor and limited to a slight darkening of the picture.
But Sony's active 3D glasses, up to now, have been different. When using the company's HDTV 3D glasses, a 3D image on the Sony displays we've tested doesn't darken as you tilt your head from side to side. Instead, the left and right images break up, producing significant 3D crosstalk or, as this artifact is more colorfully known, ghosting. In addition, the Sony's 3D color varies with head position, shifting reddish with a tilt in one direction from vertical and bluish in the other. The latter effect makes it impossible to do a reliable 3D calibration; one eyepiece of the 3D glasses has to be placed over the lens of the measurement meter for a 3D calibration, and even a slight tilt can affect the result. Fortunately, the Sony 3D sets we've tested recently have produced visually satisfying 3D color even without a 3D calibration, though it's unlikely to be accurate. Nevertheless, the head-tilt ghosting and color shifting are annoying.