As to what issues and or problems with Apex. Every device has troubles at some point or another. Probably more during the initial end user learning curve. Mistakes will happen, connections will be wrong, and integration into ones home network may be an issue. My point here is things happen and you should plan for them regardless of what eco system you choose. I have them with my ReefAngel and also my new Apex. Having said that I can say after using their customer support it has been nothing but positive and timely problem resolution. Honestly, nothing but good.
But...not all is perfect if I was being truthful. The one thing I didn't understand and makes no sense to me is some of the ways they troubleshoot. For example, I have the new Cor-15 return pump. I spent a day trying to get it working via apex but it would never see it in modules yet it would power up and run. I just couldn't control it. Support was quick, helpful, and in the end sent out to me a new cable. This didn't make sense because if we start shipping pieces rather than a full unit, it would be cost prohibitive over time. At least in my mind. Anyway I swapped out the cable, still no luck in getting my Apex to see it. So this was sent 2 day mail. I reply to my open ticket and got a call back by Luis within 5 minutes of sending it. Now the "support is great, honestly bit". They called right away after I updated the ticket with regards to the cable not working. Asked for remote connection in, I set it up, and he proceeds to connect to the "local" apex rather than via Fusion portal and saw the problem. Somehow during all of this I lost the communication / authorization / token. Once he reset that and linked, Cor-15 module found, problem solved.
So yes, support if fine but we all have bad days and bad service. I, on the other hand, while not agreeing with their debug via 2 day mail deal, resolved it and was quick to respond to communication(s). I can't say how many support people they have, I can't say how large the company is, nor can I saw how many different versions of Apex controllers are out there. What I can say is based on my experience that is how I view the company and their support. I would recommend them if you are looking for a single eco system that expands with your future growth.
Note: My first Apex was their Neptune / X10 combo back in 2000. It was a reliable product back then with similar support. To the point when I called them talking about my young GSD chewing on the main unit thinking it was a chew toy. The reply I got back after some tips on fixing a few things is that his great dane, I think it was, did the same thing. Small world.