I was thinking about this today, and I realized this same algo could lend itself to reflective shadowmaps easily. Just render the albedo and normal of surfaces when generating your shadowmap, and when doing the screen-space gi, test your rays against the reflective shadowmap instead of from the Gbuffer. This is nice because it is in worldspace, and isn't affected by screen-space discontinuities, as occlusion and such. This is terribly light bleeding prone though, and it would probably be limited to only one light source or a couple few for performance reasons. I could see this done this way. Render your scene and do all the lighting exept for the sun. Then, render the sun's shadow map with albedo and normals, do the screen-space-RT-reflections much like in killzone but use samples from both the Gbuffer and the reflective shadowmap, than add the sun lighting contribution deferredly later (so that things in screenspace lit by the sun don't give out double bounce). Some form of cheap world-space occlusion could be needed to avoid too much light bleeding though, that could be a voxelized version of the scene precomputed or dynamic, or distance fields as in the samaritan demo, or whatever else.
