Ben Brooks has a spot-on comment on task managers after his move to 2Do:
That is: if you are using every part of the task management system when things are light, then problems will arise when things get busy. It’s not that OmniFocus was overkill for me, it’s that it was too rigid. That rigidity is great when I am suffering decision fatigue from the amount of work I have, but it is a burden when I am not suffering that fatigue.
Further: when you aren’t busy your task management system should be easy. The system should scale, not permanently be operating as if you are the busiest person in the world all the time.
At its core, this is what I love about 2Do: its flexibility makes it either extremely simple or incredibly advanced – or both at the same time if you just switch views in the app. Unlike other task managers, 2Do adapts to your needs.
(Side note: after Email to 2Do, I wouldn't mind paying for all sorts of optional add-ons in the app.)