I use reminders via Siri all the time now. I find them very useful.
If I happen to read an ad, flyer, or whatever regarding some event it is so easy to tell Siri to remind whenever it is, or before. My default reminders list is Reminders so all ad hoc stuff goes in there. Or any quick reminder like that too. Works great.
I also have started using it more and more for shopping lists. For instance I have a Groceries reminder list. If I tell Siri "Add coffee to my Groceries list" she will add it to that list. Ditto for other lists.
I also use location reminders. Just yesterday, since I knew I would be going to the grocery store, I said "when I arrive at Smith's Supermarket remind me to pickup red box movie" and it went off just as I got there.
What I have done for some locations is add a second address, with a custom label: GPS Address, added by adding my current location to the contact while I am at it. Sometimes I find the GPS location for a given home or business is not exactly at the listed address. Even my own home. The GPS part works fine, as I can see it in sat view in Maps. But Maps "thinks" the street address for my home is two houses down. Ergo if I created a "when I leave home" reminder it would go off when I passed the house two houses down--IF I went that way (If I went the other way it would not go off). But by having a GPS address and choosing to use that one as my "home" reminders like that work fine now. We really need a GPS coordinates field in contacts that would take precedence over the listed street address IMO.
Michael