With Mountain Lion, Reminders no longer resembles a task-management (to-do) app in any way. I used to be able to limp along using it for my to-dos (although it never did accommodate this need well). This upgrade has made Reminders completely unusable for task management.
Once I got over my disappointment, I did some research and decided to try "Things." This application has all the functionality I've been wanting all along. It has a Mac version, an iPhone version, and an iPad version (among others)--and it keeps all devices synched via the Cloud (just not the iCloud ... but who needs the i ?). I wish I'd discovered it years ago. I'm glad now that Mountain Lion put Reminders over the edge; otherwise, I would not have made this discovery.
"Things" (oddly named though it is) comes close to the old Franklin planner software I used to love and haven't been able to find a substitute for. It can import items from Reminders, and it works with Siri. It's a joy to use, and it does everything I want it to do plus some things I never thought of and will use all the time. I downloaded the free trial version last night and within an hour paid for it with gratitude.