I have the ACII, and for the amount of money I spent on it, I'd have to say that I'm not very satisfied. The PH probes I got were defective and had to be sent back to Neptune for testing, at my cost. I've re-calibrated the current PH probe several times, but I still don't trust it (it reads 7.8-8.05; I dose 2-4 tsp. of Kalk a day and my dKH is 10.25); also, the ORP probe usually returns a reading greater than 450, and sometimes as high as 490. Needless to say, I wouldn't feel confident having it control a kalk/calcium/ozone reactor, which is half the point of getting an all-in-one-controller. The AquaNotes software is glitchy (even with the latest patch) and it was not very easy to sync up the controller to my computer. Any time that I want to reprogram the controller, I have to do a manual re-boot by taking the battery out and cutting the power. When it resets, I lose all the programmed information and the clock reverts back to midnight, so all the programmed devices go into chaos. I do have the DC8, which I'd say is a must if you're planning on controlling your lighting. If I could go back in time, I'd buy an Aquatronica. They're expandable (which the AquaControllers are not) and seem to be more stable & reliable.