What are some alternatives?
When comparing Effitask and todotxt.net, you can also consider the following products
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Markor - Text editor - Notes, ToDo & Bookmarks. Markdown and todo.txt support.
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
Nozbe - Nozbe - to-do, task, project and time management productivity gtd getting things done online application with software for Apple iPhone iPad Android Mac Windows Linux
Remember The Milk - Remember The Milk is a task and time management application for mobile devices.
Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.