I use Siri to set alarms and timers since that's far and away more convenient than opening the app and switching to the right tab and futzing with the time dial.

If I've got my phone in my pocket and my hands full it's helpful to be able to tell Siri to turn the flashlight on.

Aside from that I don't think I've used it for much. I get the weather from the radio already, and don't care to search the web with a voice assistant. It'd be nice if she'd read me my text messages but she flatly refuses to do that.