I absolutely love the redundancy of the extra temperature probes to save me from a heater malfunction, the ability to check it for peace of mind from anywhere, and the extra outlet! Being able to program a backup heater instead of running simultaneously by setting them to different threshholds is clutch to keep heater wear down.
And the water testing?? Who wouldn't want a quick and convenient read on what they are about to add to their Water box, or how the water in the box is. Even if you already have one, this device is so affordable its worth getting another to check against for accurate reads and keeping things calibrated. It checks everything i want to know during a water change, and that is an awesome thing.