I used to manage the network at a co-working space and I had two of these access points installed in a mesh setup, with one covering the main front room, and one covering the back part of the building.

I'm not sure if it can handle 500+ concurrent users, but we would frequently have as many as 100 people present and on the WiFi during some of the events we held, and we never had any issues. We would have people live streaming video while other people were working on their laptops. As the network admin, I regularly did speed tests and asked people how the internet was working for them and everyone was always very happy with it.

Over the course of about two years, we had over 3,000 people log into the WiFi, and never once had a single problem (other than from our main gigabit cable internet going down once or twice).

This is a HUGE contrast from my experience with consumer grade WiFi routers like Linksys, Netgear, and D-Link, which often advertise crazy speeds like 2,000 Mbps but only deliver 50 Mbps in real life. I once had a $300 D-Link router that I literally had to reboot every week or else it would become completely unusable and slow to a crawl, for example.

Ubiquiti is still pretty good for home usage. Their gear is the only one I have used so far that handles 10-15 active devices without breaking a sweat. Other APs I've tried fall apart pretty quickly at that number.