If you are planning on using Todo with Dropbox, iCloud, Toodledo, or Wi-Fi (Wi-Fi option syncs with Todo for Mac), this is the app you want. The standard Todo app is a paid app available on the App Store and on the Mac App Store. This app also includes an option to sync with our new Todo Cloud service, but this is meant as a convenience to those of you that want to switch to Todo Cloud.
Todo Cloud is a new collaborative productivity service with free companion apps available for the iPhone, iPad, iPod touch, and the Mac. Todo Cloud includes all the basic features found in the standard Todo app. Todo Cloud gives you access to your tasks in all major web browsers, lets you create shared task lists, and lets you create tasks using Siri on your iPhone, iPad, and iPod touch.
Basic access to your Todo Cloud tasks from a web browser will always be free. A Todo Cloud premium account is required to sync with any of the free Todo Cloud apps. When you first create an account on www.todo-cloud.com, you'll get 14 days to try out the premium features for free. A full comparison of basic and premium accounts can be seen here.