They work great, but as Alton said, it's just something else that can go wrong. I came home a few times to that the reactor had run dry becaue of a plumbing leak and co2 was being directly injected into the water supply. I can only imagine what the ph was in the tank, but I was too scared to check.

Troy has a good point, my ph went from 8.0 to a constant 8.2-8.3 when I switched mine off and went to dripping kalkwasser.