I've been using the Apex controller for my reef for years, and for the most part once it is set up, I don't touch it. If it works, I'm happy. Occasionally I get motivated to make some changes, be it because some equipment has failed and had to be replaced, or something was upgraded. I tend to resist change, believe it or not. I know that sounds odd from a guy that tries out new products and loves gear, but when you reef is happy you normally don't change anything to avoid causing problems.
I use the Apex to turn various pieces of gear on and off, to get alerts when certain items are out of range, and to track water parameters.
For the last decade, I've been using Neptune System's Aquacontroller. First I had the AC II, then later upgraded to the AC 3. Near the end of 2011, I gifted myself the Apex controller, the latest available version at that time. The Apex has been around for a couple of years, and many of my friends swear by it.
This month's club meeting included a visit from Dave Botwin who did a really nice presentation about how to use inexpensive parts to make your Apex controller more handy. I had to pick him up from the airport and after he was done gazing at my tank, we talked about what kinds of things I'd like my Apex to do that it doesn't do already. The first hurdle was overcoming my trust issues regarding the return pump. I've always had that plugged directly into the a wall outlet so nothing could disable it other than a full-blown power outage. No GFCI outlets, just keep it powered at all costs.