I have to say that for simple reminders, it's OK. If you have a list of things to do without reminders though, it is pretty worthless if your list grows beyond a few items.
I've really tried to find a way to make it work for me. I've been using ToDo, though I haven't come close to really taking advantage of its features. I thought maybe I'd be able to replace it with the new reminders app. Unfortunately, I just cant. Even messing around with priorities for tasks, I just can't find a way to make it usable. It's a shame really.
Add to that the fact that I see some really strange behavior when syncing reminders to an Exchange 2010 environment. I have an iPhone, iPad, iMac syncing to Exchange using Mail and iCal and Outlook 2011, and Outlook 2007 on the office PC.
The ONLY place the due and reminder dates and times are correct are on the device where they were first created.
I create a task for tomorrow on the phone, and it shows up as due today on the iPad. Shows as tomorrow in Outlook on the office PC, but due at midnight instead of 5:00PM. On the iPad, the reminder is set to go off a day after it's due. And it gets worse if I try to "fix" it.
Tasks synced with iCloud sync and work fine, but again, I can't really manage the things that need to get done.
I've relegated it to the last page of my iPhone and iPad along with News Stand, hoping for improvement in the future. I'll just keep using ToDo for now.