ironically I use her almost daily for all of these with well over 90% accuracy. I would feel a little insincere saying "99%", but I honestly can't remember the last time she failed.
The only "come the fuck on siri" that I've hit is since Apple Music... whenever you have something loaded up in background audio (apple music, sound cloud, shazam, etc).. if it's not playing, but still loaded up, and you ask siri "what song is playing?" wanting her to identify a song playing say in a club or the car or something.. she will identify the song still in memory in the background audio app.
but outside of that.. calendars, notes, alarms, timers, and maps on both my phone and watch have been flawless for longer than I care to remember now.