I'm going to be the nay sayer here. I had used the Apex for about 6 years . I had tanks without the Apex for about 9 years. When I moved to Cali from Portland and set up my new little 50g tank, I left the Apex in the closet, about 15 feet from my tank.
The best part for me is the one button to feed button to turn off the power heads, return pump, and the protein skimmer. When the display unit broke for the second time (replaced it once) and I had to use the phone app that stopped being so great.
If you are using it to monitor your calcium reactors pH, it is handy for that. I run my CA reactor very old school so that was never a thing for me.
I had mine setup for to warn me if something went wrong, but when something went wrong (power out) the internet for the house went off as well so, it could not warn me. What saved my system that day was the $75 battery back up that runs my vortech. The Apex did not come into play.
I also had mine setup for temperature control. Cascading things like the white lights would turn off, fan turn on, chiller turn on, blues turn off, etc etc. But I also have my central air to go on at 74F, so that never came into play for me.
Turning the heater off in case of failure can be handy. I run a series of small heaters, and I buy nice heaters, so one heater being stuck on is not going to nuke my tank as it is.
Really the Apex is just a fancy timer (unless you are using it as a pH probe then it is a fancy timer with a pH probe). Before the Apex I ran my systems on those little plug in timers you get at $5 from target. With the gear now you don't even need those, except as a back up on the ATO or if you run a stand exhaust fan. I went back to my American DJ powerstrip and computer system battery backup on the vortech.
IME the Apex is a nice toy, but it really doesn't do anything that amazing for most reefers. I have not tried the Trident system, that might be a game changer for some people but I don't see it as much more than a re-branded dosing pump.
JMO