It's so easy to use, and to categorize your tasks, but where Errands shines is the subtle yet highly efficient way it reminds you on a very consistent basis when you need to do something. There are no loud alarms, just a very subtle audio and visual reminder, even when the app is not active. It's just works, and integrates into your life so well, that I cannot but help recommend you check it out.
Errands for iPhone