Things' lack of reliable, convenient syncing killed it for me. OmniFocus, while not as sexy and certainly more complicated than Things, has rock solid syncing t

Things' lack of reliable, convenient syncing killed it for me. OmniFocus, while not as sexy and certainly more complicated than Things, has rock solid syncing to your iPhone or Mac via MobileMe or any other webdav server you choose. And its robust configurability means you can set up a very Things-like workflow if that's your bag. And the iPhone version is sweet! If you want to have todos available in more than one place, Things will bring you nothing but tears.