I can’t seem to get them to work reliably, but then I could be doing something wrong, I dunno.
I got through three of them last winter, each one ended up with a completely seized piston, which makes them squeally and rubbish at stopping you. I tried cleaning them thoroughly and changing the pads, manually pushing the pistons in and out a few times, lubing the pistons with DOT fluid, re-bleeding, stripping down and using that red rubber grease stuff to lube the seals, and even a complete piston and seal replacement. Some of those things worked a bit, but the problem always came back after a couple of rides.
I bought a third one cheap in January to see if I’d just got a duff batch on my bike, but that one went the same way after a couple of months. I’m sure they’re great in other places but they just don’t seem to like the mud round our way (Dark Peak/South Pennines).