I've plugged this here before: I am a big fan of Tracks (http://getontracks.org/ http://getontracks.org/). I think I fall much more on the featureful side of th

I've plugged this here before: I am a big fan of Tracks (http://getontracks.org/ http://getontracks.org/). I think I fall much more on the featureful side of the spectrum than people who like the text file approach or something spartan like Gmail tasks. I'll have to check out Todoist - it sounds like they offer nice grouping features, which is something the vast majority of apps are badly lacking.