I've been using Moo.do for the last few weeks, and I love it. The keyboard shortcuts are fantastic, and the ability to create infinitely nested lists is what really separates it from other apps like Wunderlist, Asana, and Trello. No more deciding where something belongs in the binary world of top-level todos and subtasks - with Moo.do, you can nest sub-sub-subtasks where they belong.
Another thing I really love about Moo.do is the ability to quickly shift perspective to focus on different levels of a project. With ⌘ + enter, I can quickly drill deep into a project to focus on a single item, and then with ⌘ + shift + enter I can just as easily climb up the project tree to see everything.
It's powerful without being overly complex. It's available on every device... and it has great keyboard shortcuts! Give Moo.do two days as your primary tool. You won't regret it.