I've never used it nor do I know of any games that use it. You'd think it would be more popular because if you cach correctly, you don't have to render new data every frame and everything can be calculated per vertex not at the pixel level. All this adds up to a faster framerate for shadows, motion blurs and DOF. There has to be a caveat somewhere.
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Yes i know.

Do you mean reverse reprojection caches, to optimise pixel shading costs?
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Yes exactly.

Can't remember exactly where I saw those examples... maybe Crytek and Epic?
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i think u are right .

GPU pro 2 has a chapter in global Illumination effect with name of "Temporal screen-space ambient occlusion" that using Reverse reprojection but it is too abstract and complex to understanding.
And also in game engine gems 2 , chapter 7 "a spatial and temporal coherence framework for real time graphics" describes more than gpu pro but still it is so complex!