What do you like best?
the CLI is hands down the most intuitive I have ever seen. Once you're practiced, it's the quicked way to do anything.
The commit confirmed feature is completely underrated. Barracuda, PFsense, Sophos, anyone... look at Juniper. That's how you create a firewall.
What do you dislike?
Basic things like QoS is not something trivial on a Juniper. At least not on an SRX...
I've tried my luck and failed. You need courses to be able to do something other firewalls offer a checkbox for.
What business problems are you solving with the product? What benefits have you realized?
Security, Performance with the vSRX, scalability, ease of use for standard things.