First off, I'm an software engineer and I love gadgets. And I don't have an Apex. I didn't get an Apex to start, honestly, because I didn't know how serious of a reefer I'd be. I'm still a technically a rookie, less than a year into it, so take my suggestions with a grain of salt.
Here's what I can definitively say, You don't need an Apex to have successful, stable and functioning reef setup. I still have what some may call a non-mature tank, but so far after an early hiccup or two things have been running smoothly. And if you're curious, those hiccups were not something Apex would have helped me with at any rate. Just for the record, I'm not a believer in mature tanks, it's really more about how diligent you are at maintaining, paying attention to your tank, and applying logical/proven/sensible fixes to problems that arise (that are hopefully data driven). I buck the normal trend and I have no qualms about suggesting adding SPS from day 1 after your cycle is complete.
Here's what I have running that i believe would be covered by Apex if I had one.
* I use EcoTech lights and pumps with a reeflink, so I am able to schedule them via the web or my phone. I am pained that buying an Apex would require me to buy extra Neptune hardware module to control my lights and wave pumps (WMX controller). And even more pained that I can't control my return pump with an Apex because of incompatibility.
* I have 4 BRS dosers using Woods digital timers (almost old school) for Ca, Alk (soda ash), Mg, AcroPower
* I have a Seneye (that I really just bought for the PAR meter when it was on sale), but use for pH and temperature monitoring just for kicks - do I need it, not really. pH is somewhat useful as it could indicate something is wonky with my dosing.
* I use a Ranco temperature controller to handle an errant heater.
* I have a tunze osmolator 3155
And probably the most important thing is, while I don't chase numbers, I monitor my tank like a hawk, but I'm odd, I actually enjoy testing alk.
That's pretty much the only number I test for regularly. Next is phosphorus, and then nitrate. I also keep an eye on my ATO and dosing containers to make sure they're not empty.
If I did it again would I get an Apex, maybe, maybe not. I am in the process of contemplating an upgrade to a 200 gallon tank and I'm looking into an Apex as an option. I still haven't convinced myself I need one.