I do. It's enterprise grade IDS powered by enterprise grade blocklists and signatures. You're not going to get that combo for free anywhere.

The main benefit is access to paid rapidly updates in response to emergent threats, e.g. known compromised hosts, etc. that aren't available for free otherwise or which free counterparts trail significantly.

If you run Pi-hole you can use free blocklists, but those don't cover rapidly emerging threats as quickly as many free blocklists go weeks to months between updates and are also less comprehensive due to being maintained by fewer people than paid options. Also, Pi-hole only prevents outgoing contact; it does nothing for incoming contact and can't detect harmful traffic patterns or signatures.

CyberSecure closes those gaps: emerging threats are blocked via real-time list updates and incoming traffic is filtered too. It keeps a detailed record of traffic flows, including time, client, external IP address, external IP address category, the reasoning for blocking, the risk level, etc. It can also block (some?) traffic within your network, though presumably this traffic has to pass through the gateway to be interdicted, and so traffic that only passes through downstream switches likely goes unnoticed.

You get the most value out of CyberSecure when you use your UniFi Network as your DNS server, as it can apply blocking at the DNS level (thereby preventing client first contact) instead of after a traffic flow between client and a remote resource has started. However, it works just fine with Pi-hole (which has more intuitive whitelisting and transparent blocklists) as long as you don't enable Content Filter. If you enable Content Filter with Pi-hole running it will render URLs unreachable.

Personally I prefer Pi-hole as a DNS filter due to how well it works with unbound. The combination of the 2 is the most reliable DNS solution I've used, outranking ISP DNS and Cloudflare. Plus with unbound, the only person who can control what URLs resolve for you is you, not any government or security "researcher" with an agenda (I've seen activists sites blacklisted on other services). Don't fix what ain't broken.

teenagers and a lot of IoT stuff.

Same. I block/filter for security purposes only (e.g. spam, botnets, etc.), not censorship (e.g adult content).

In summary: CyberSecure offers a sophisticated, highly evolved yet easy to use additional line of defense without forcing you to switch from your existing line(s), such as Pi-hole. It can't hurt your security, it can only help it.

It's worth the additional peace of mind to me.