Not redundant but I'd also take a look at Omnifocus.
Do you really only want a mobile or web version of your lists? Unless I missed it there is no desktop version so it depends on net access to run on the main computer.
Will you ever have items in your lists that are private or need to be stored securely?
Do you always have access to the internet where you are?
I would second looking at Toodledo if you are comfortable with on-line and cloud based task managers.
Oogie McGuire - Mac, iPhone & Omnifocus
OogieM on Twitter
Paonia, CO USA