The built in Reminders app was not sufficient for what I was looking for in a task manager, so I tried a handful of the more popular and well-regarded ones here. Out of the bunch, OmniFocus was the standout.
OmniFocus has its own ideas about how it should/can be used. To get the most out of it you need to buy into its concepts of actions, projects, action groups, sub projects, folders, and contexts.
If you can do that, you will find it can be a very powerful and intuitive tool. If not, you may get frustrated because how some of the features work is not always intuitive. In other words, expect a learning curve if you want to learn its nuances and get the most out of it.
There are some quirks between the iPad an iPhone versions. You can, for example, create an action directly inside a subproject on the iPhone. But on the iPad there does not seem to be a way to do that; you have to create the action one level up and then move it in a second step into the subproject. Not a deal breaker but it does deter from an otherwise polished product.
I have also experienced crashes on occasion with this version. OmniGroup seems to be quite active in updating and updating their products so I expect this to become a non-issue.
I have contacted OmniGroup customer support on a couple of occasions and the response and timeliness has been excellent.