For me, there are some criteria for any to do list tool:
- It must have a website version, a compatible Android app and an iPhone app.
- It must have recurring tasks.
- It must 'feel' right.
I eventually settled on Producteev. This seems to meet all of my criteria. I like the way I can create different workspaces, so my home tasks don't appear at school. Although I don't take advantage of the facility, you can collaborate with other users. Adding subtasks and notes is easy too.
It could be improved by allowing tasks to repeat from the completion date, not just from the due date. But for now I'm happy with it.