Yeah cgminer does work with these cards, ive been testing it now and then, but have always returned to chainminer. The reason is that even though the speed looks very good after a while it tunes itself to max speed (385GH/s vs. 420GH/s max speeds, chainminer vs cgminer), after a day or so it goes below chainminer speeds. I guess restarting cgminer daily would fix that, haven't really bothered as chainminer just rolls on on autotune. And cgminer does have some options to tune bitfury cards manually, but currently i just want my rigs to run without constant tuning .