The DF piece on it pretty much sums it up. It looks terrible when maxed out and its fixed cost of 10ms on average make it essentially useless for what it does. It is however interesting how will different games with official implementation look like. Maybe if it did more than screen space it would be what people make it out to be?
edit: there absolutely is a "developer cost" to it in order to get plausible effects. Otherwise it's just a slop filter leaving the geometry and such untouched







