It's fast, native and simple. Also the design is beautiful

I like being able to drag just about anything into the interface and create a task that references back to the source. For example, I get an email that is essentially a task. I can drag it onto things and it creates a task that I can name and schedule. In the task itself is a link back to the email, so when its time to do the work, I can click the link and have the email pop right up. This completely eliminates my need to manage my inbox at all. The fact that this feature even works when syncing across two computers is fantastic.

Actually helps me get everything out of my brain so I'm not wasting energy remembering little things, while at the same time it let's me organize major projects and goals for myself and various teams I working with.