I use cable cutters regularly in my single break dual deploy md flights. I've only had one issue with a cable cutter flight (a blackhawk38 flight years ago) but that was due to an issue with electronics, not the cable cutter. I use them in a non redundant configuration from 54mm and below and for 75mm I use them in a redundant configuration. So I have two cutters per one zip tie so even if one fails the zip tie still gets cut in bigger rockets. I always use 0.3 grams (grains, whatever, I use the measured vial) instead of the 0.1 recommended to ensure the zip tie cuts. Sometimes I've had issues with getting the pistons out because of how energetic the charge is in such a small enclosure. I've found tapping the non threaded end of the cylinder with a slightly larger diameter drill bit (but still much smaller than the piston) I can knock out stuck pistons more easily. Personally I reckon the chamfered pistons are unnecessary but I've yet to cut over to solid slug cylinders which I reckon would work better. I've got it under good authority that the original cable cutter Archtype's model was based on had this style design.
Two caveats. First, always seal the threaded screw end where the ematch is seated with hot glue. That pretty much eliminates bp leakage which could cause a sub-optimal recovery. Two, always incorporate a swivel on your recovery harness about 1/3 of the way down from the NC (in terms of total harness length). I suspect that if you don't use a swivel the chances of a tangle and therefore unsuccessful main deployments go up quite substantially.
