I only use it to set timers and it sucks at that half the time, not even going to bother with the faff of doing anything more complex. It's quicker to just do it myself as I'll probably have to unlock the screen anyway.

"Siri, timer, one hour thirty"

"Timers can't be set for a time of day, so I set your Timer alarm for 1:30"

Every damn time. Siri hates Brits.