I'm now happily using Todoist. The free version is somewhat limited (no task notes, no reminders), and paid is a bit pricey (US$ 29,- / year). But on the other hand, I've come to really appreciate some of its features, such as breaking up tasks into subtasks, further grouping in projects (eg. I've got a tree like "Work / $ProjectX", "Home and Family", "Private / Hacking", "Private / $VolunteerWork", etc.). I found it especially helpful to be able to break up a task into subtasks. This makes it easier to break down complex and/or blurry tasks down into manageable, low-barrier pieces. Which in turn helps remove some angst around starting said complex / blurry task.
Also, for all it's functionality, the UI is remarkably uncluttered, and it also has decent keyboard support. UI-wise, I also like how colour is used (and can be customized) to give visual cues on what to focus.
Plus: sync is flawless.