I find that the APEX by itself is a reasonable value compared to other premium monitoring systems. Coralvue Hydros might end up being a value competitor, but as someone who has used both...Apex is still slightly better and offers a better experience IMO. Definitely shows promise if they keep improving and adding options.
I would say if I were to give up my Apex it would be due to the escalation of costs that tend to come with having an APEX environment. The APEX itself is nifty, albeit $$$. I mean with a lot more effort and patching together a half dozen products you could probably accomplish what the APEX does at a fraction of the cost. However, APEX really is a seamless experience that has you up and running in minutes all under one interface. I think it is worth it, especially with the EL versions lowered entry price.
But...the true value of the APEX is all the stuff you can eventually do with it. Water testing, dosing, lunar cycles, fluid controls, etc. etc. Once you get the base unit set up you find yourself wanting to do more, and each of those additional features is very expensive because just about nothing APEX sells is under $100. A $600 Trident here, a $200 ATO kit there (even though you already had one but wanted an APEX ready one so you could integrate better...silly you). If this syndrome doesn't take you, I think in addition to selling to upgrade or get out of the hobby, there are some people that come to realize after a while that they are really only using it to control the temperature and a few probes. You don't need an expensive controller to do that...so they cash out because APEX gear retains value remarkably well. This is especially true as more lights, powerheads, and other equipment come with their own purpose-built control software eliminating some of the need for a robust controller.