[imsaar]

I am using Toodledo.com (very ugly web interface but good functionality) with Ultimate To Do iphone app which can sync with Toodledo and it has been working out pretty well.

I agree a To Do list that is not always with you is not an effective list.

I have tried all the ones you mentioned except Todoist and none of them is as effective as my current solution.

Another nice thing with Toodledo is that they have a good and simple API that can be used to make it available on other smartphones as an offline app.