Stereo instancing with deferred rendering mode result in incorrect lighting, and differences in coloration between the left eye versus the right eye. The geometry looks unlit. Geometry in the left eye looks like its color is a combination of the single directional light in the scene plus the ambient color (though no shading is apparent). Left eye geometry looks like it is colored only by the ambient color. The background color differs from one eye versus the other.

None of these problems happen using multi-pass or single-pass stereo. See attached screen shots.