My trust of what Siri is capable of is laughably low but I do use it for reminders ("Remind me on X day...", "Remind me in X hours...", "Remind me when I get home...") and for timers. Occasionally I'll use it for unit conversions but I usually use Alexa for that since I'm in my kitchen often when I use that and it's just right there. Other than that I don't use it.