OmniFocus

It's very user friendly, I mean, that's my general impression and they've got a very healthy set of connected services. One of the things that stood out to me in my experimentation with it is the easy way in which it displays the available actions. For anything that's local, at least on an iPhone, I just use my Pushka Automation server. And then off you go, it just handles it for you because I've already got a shortcut. It doesn't require your Mac to be turned on, but as with all web services, it needs to be connected to web services.