Oh, and saying "What's my name" and having Siri respond "Your name is <name>, but since we're friends I get to call you Captain James T Kirk". But that's just personal amusement.
I use it for stuff I forget to buy when I'm shopping, mostly. The stuff you don't buy often, like "remind me to get deodorant when I'm at Kroger."
Also the timer-type reminders/alarms are great.
I really wish it was easier to compose notes and the like. I finally found how to reliably get a newline with the voice keyboard (by saying "period newline"...the period is required).
"Her" was pretty inspiring for all of the voice-related stuff. But I'm still weird about using voice commands in public. If everyone was, I'd get over it.
Seems a lot more suspicious of me for some reason..